Survex data files

Survey data is entered in the form of text files. You can use any text editor you like for this, so long as it has the capability of writing a plain text file in UTF-8 or ASCII encoding. The data format is very flexible; unlike some other cave surveying software, Survex does not require survey legs to be rearranged to suit the computer, and the ordering of instrument readings on each line is fully specifiable. So you can enter your data much as it appears on the survey notes, which is important in reducing the opportunities for transcription errors.

Also all the special characters are user-definable - for example, the separators can be spaces and tabs, or commas (e.g. when exporting from a spreadsheet), etc; the decimal point can changed to be a comma (as used in continental Europe), or a slash (sometimes used for clarity in written survey notes), or anything else you care to choose. This flexibility means that it should be possible to read in data from almost any sort of survey data file without much work.

Survex places no restrictions on you in terms of the ordering of survey legs. You can enter or process data in any order and Survex will read it all in before determining how it is connected. You can also use the hierarchical naming so that you do not need to worry about using the same station name twice.

The usual arrangement is to have one file which lists all the others that are included (e.g., 161.svx). Then cavern 161 will process all your data. To just process a section use the filename for that section, e.g. cavern dtime will process the dreamtime file/section of Kaninchenhöhle. To help you out, if the survey has no fixed points and you are using Survex’s default unspecified coordinate system, cavern will pick a station and fix it at (0,0,0) (and print a info message to this effect).

It is up to you what data you put in which files. You can have one file per trip, or per area of the cave, or just one file for the whole cave if you like. On a large survey project it makes sense to group related surveys in the same file or directory.

Readings

Blank lines (i.e. lines consisting solely of BLANK characters) are ignored, except that in interleaved data a blank line ends the current traverse.

The last line in the file need not be terminated by an end of line character.

All fields on a line must be separated by at least one BLANK character. An OMIT character (default -) indicates that a field is omitted. If the field is not optional, then an error is given.

Survey Station Names

Survex has a powerful system for naming stations. It uses a hierarchy of survey names, similar to the nested folders your computer stores files in. So point 6 in the entrance survey of Kaninchenhöhle (cave number 161) is referred to as: 161.entrance.6

This seems a natural way to refer to station names. It also means that it is very easy to include more levels, for example if you want to plot all the caves in the area you just list them all in another file, specifying a new prefix. So to group 3 nearby caves on the Loser Plateau you would use a file like this:

*begin Loser
*include 161
*include 2YrGest
*include 145
*end Loser

The entrance series point mentioned above would now be referred to as: Loser.161.entrance.6

You do not have to use this system at all, and can just give all stations unique identifiers if you like: 1, 2, 3, 4, 5, … 1381, 1382 or AA06, AA07, P34, ZZ6, etc.

Station and survey names may contain any alphanumeric characters and additionally any characters in NAMES (default _ and -). Alphabetic characters may be forced to upper or lower case by using the *case command. Station names may be any length - if you want to only treat the first few characters as significant you can get cavern to truncate the names using the *truncate command.

Anonymous Stations

Survex supports the concept of anonymous survey stations, that is survey stations without a name. Each time an anonymous station name is used it represents a different point. Currently three types of anonymous station are supported, referred to by one, two or three separator characters - with the default separator of ., that means ., .., and ... are anonymous stations. Their meanings are:

Single separator (. by default)

An anonymous non-wall point at the end of an implicit splay.

Double separator (.. by default)

An anonymous wall point at the end of an implicit splay.

Triple separator (... by default)

An anonymous point with no implicit flags on the leg (intended for cases like a disto leg along a continuing passage).

You can map - to .. (for compatibility with data from pocket topo) using the command:

*alias station - ..

Support for anonymous stations and for *alias station - .. was added in Survex 1.2.7.

Support for anonymous stations in the cartesian data style was added in Survex 1.4.10.

Numeric fields

Measurements start with an optional PLUS or MINUS character (+ and - by default), and have an optional decimal point (represented by a DECIMAL character, default: .) which may be embedded, leading or trailing. No spaces are allowed between the various elements.

All of these are valid examples: +47, 23, -22, +4.5, 1.3, -0.7, +12., 23., -34, +.15, .4, -.05

In formal syntax that’s either:

[<MINUS>|<PLUS>] <integer part> [ <DECIMAL> [ <decimal fraction> ] ]

or

[<MINUS>|<PLUS>] <DECIMAL> <decimal fraction>

Accuracy

Accuracy assessments may be provided or defaulted for any survey leg. These determine the distribution of loop closure errors over the legs in the loop. See *SD for more information.

Cavern Commands

Commands in .svx files are introduced by an asterisk (by default - this can be changed using the set command).

The commands are documented below in a common format:

  • Command Name

  • Syntax

  • Example

  • Validity

  • Description

  • Caveats

  • See Also

ALIAS

Syntax

*alias station <alias> <target>

*alias station <alias>

Example
*begin parsons_nose
*alias station - ..
1 2 12.21 073 -12
2 -  4.33 011 +02
2 -  1.64 180 +03
2 3  6.77 098 -04
*end parsons_nose
Description

*alias allows you to map a station name which appears in the survey data to a different name internally. At present, you can only create an alias of - to .., which is intended to support the pocket topo style notation of - being a splay to an anonymous point on the cave wall. You can also unalias - with *alias station -.

Aliases are scoped by *begin/*end blocks - when a *end is reached, the aliases in force at the corresponding *begin are restored.

*alias was added in Survex 1.2.7.

See Also

*begin, *end

BEGIN

Syntax

*begin <survey>

*begin

Example
*begin littlebit
1 2 10.23 106 -02
2 3  1.56 092 +10
*end littlebit

; length of leg across shaft estimated
*begin
*sd tape 2 metres
9 10 6.   031 -07
*end
Description

*begin stores the current values of the current settings such as instrument calibration, data format, and so on. These stored values are restored after the corresponding *end. If a survey name is given, this is used inside the *begin/*end block, and the corresponding *end should have the same survey name. *begin/*end blocks may be nested to indefinite depth.

See Also

*end, *prefix

CARTESIAN

Syntax

*cartesian grid

*cartesian magnetic

*cartesian true

*cartesian grid <rotation> <units>

*cartesian magnetic <rotation> <units>

*cartesian true <rotation> <units>

Example
*cartesian magnetic

*cartesian true 90 degrees
Description

*cartesian specifies which North cartesian data is aligned to, and can optionally specify an extra rotation to apply. The default is that it’s aligned with True North.

Notes on the different North options:

GRID

North in the current input coordinate system (as set by e.g. *cs UTM30). If no input or output coordinate system is set then this is the same as TRUE since in Survex’s default unspecified coordinate system True North is the same as Grid North.

MAGNETIC

Magnetic North. If using automatically calculated declinations then this will be calculated at the *date in effect for each cartesian data reading.

TRUE

True North. If no input or output coordinate system is set then this is the same as GRID since in Survex’s default unspecified coordinate system True North is the same as Grid North.

*cartesian was added in Survex 1.4.10. Prior to this cartesian data was documented as aligned with True North, but if an output coordinate system was specified it was actually aligned with this (which was not intended and doesn’t really make sense since changing the output coordinate system would rotate cartesian data by the difference in grid convergence).

See Also

*cs, *data cartesian, *date, *declination

CALIBRATE

Syntax

*calibrate <quantity list> <zero error>

*calibrate <quantity list> <zero error> <scale>

*calibrate <quantity list> <zero error> <units>

*calibrate <quantity list> <zero error> <units> <scale>

*calibrate default

Example
*calibrate tape +0.3
Description

*calibrate is used to specify instrument calibrations, via a zero error and an optional scale factor (which defaults to 1.0 if not specified). Without an explicit calibration the zero error is 0.0 and the scale factor is 1.0.

<quantity list> is one or more of:

Quantity

Aliases

LENGTH

TAPE

BEARING

COMPASS

GRADIENT

CLINO

BACKLENGTH

BACKTAPE

BACKBEARING

BACKCOMPASS

BACKGRADIENT

BACKCLINO

COUNT

COUNTER

LEFT

RIGHT

UP

CEILING

DOWN

FLOOR

DEPTH

EASTING

DX

NORTHING

DY

ALTITUDE

DZ

DECLINATION

The specified calibration is applied to each quantity in the list, which is handy if you use the same instrument to measure several things, for example:

*calibrate left right up down +0.1

You need to be careful about the sign of the ZeroError. Survex follows the convention used with scientific instruments - the ZeroError is what the instrument reads when measuring a reading which should be zero. So for example, if your tape measure has the end missing, and you are using the 30cm mark to take all measurements from, then a zero distance would be measured as 30cm and you would correct this with:

*CALIBRATE tape +0.3

If you tape was too long, starting at -20cm (it does happen!) then you can correct it with:

*CALIBRATE tape -0.2

Note: ZeroError is irrelevant for Topofil counters and depth gauges since pairs of readings are subtracted.

In the first form in the synopsis above, the zero error is measured by the instrument itself (e.g. reading off the number where a truncated tape now ends) and any scale factor specified applies to it, like so (Scale defaults to 1.0):

Value = ( Reading - ZeroError ) * Scale

In the second form above (supported since Survex 1.2.21), the zero error has been measured externally (e.g. measuring how much too long your tape is with a ruler) - the units of the zero error are explicitly specified and any scale factor is not applied to it:

Value = ( Reading * Scale ) - ZeroError

With the default scale factor of 1.0 the two forms are equivalent, though they still allow you to document how the zero error has been determined.

With older Survex versions, you would specify the magnetic declination (difference between True North and Magnetic North) by using *calibrate declination to set an explicit value (with no scale factor allowed). Since Survex 1.2.22, it’s recommended to instead use the new *declination command instead - see the documentation of that command for more details.

See Also

*declination, *units

CASE

Syntax

*case preserve

*case toupper

*case tolower

Example
*begin bobsbit
; Bob insists on using case sensitive station names
*case preserve
1 2   10.23 106 -02
2 2a   1.56 092 +10
2 2A   3.12 034 +02
2 3    8.64 239 -01
*end bobsbit
Description

*case determines how the case of letters in survey names is handled. By default all names are forced to lower case (which gives a case insensitive match), but you can tell cavern to force to upper case, or leave the case as is (in which case 2a and 2A will be regarded as different).

See Also

*truncate

CS

Syntax

*cs <coordinate system>

*cs out <coordinate system>

Example
*cs UTM60S
*fix beehive 313800 5427953 20

; Output in the coordinate system used in the Totes Gebirge in Austria
*cs out custom "+proj=tmerc +lat_0=0 +lon_0=13d20 +k=1 +x_0=0 +y_0=-5200000 +ellps=bessel +towgs84=577.326,90.129,463.919,5.137,1.474,5.297,2.4232"
Description

*cs allows the coordinate systems used for fixed points and for processed survey data to be specified.

The “input” coordinate system is set with *cs and you can change it between fixed points if you have some fixed points in different coordinate systems to others.

The “output” coordinate system is set with *cs out and is what the survey data is processed in and the coordinate system used for resultant .3d file. The output coordinate system must be in metres with axis order (East, North, Up), so for example *cs out long-lat isn’t valid because it isn’t in metres, while *cs out jtsk isn’t valid because the axes point West and South.

*cs was added in Survex 1.2.14, but handling of fixed points specified with latitude and longitude didn’t work until 1.2.21. Also *fix with standard deviations specified also didn’t work until 1.2.21.

The currently supported coordinate systems are:

  • EPSG: followed by a positive integer code. EPSG codes cover most coordinate systems in use. The website https://epsg.io/ is a useful resource for finding the EPSG code you want. For example, EPSG:4167 is NZGD2000. Supported since Survex 1.2.15.

  • CUSTOM followed by a PROJ string (like in the example above).

  • ESRI: followed by a positive integer code. ESRI codes are used by ArcGIS to specify coordinate systems (in a similar way to EPSG codes) and PROJ supports many of them. Supported since Survex 1.2.15.

  • EUR79Z30 for UTM zone 30, EUR79 datum. Supported since Survex 1.2.15.

  • IJTSK for the modified version of the Czechoslovak S-JTSK system where the axes point East and North. Supported since Survex 1.2.15.

  • IJTSK03 for a variant of IJTSK. Supported since Survex 1.2.15.

  • JTSK for the Czechoslovak S-JTSK system. Its axes point West and South, so it’s not supported as an output coordinate system. Supported since Survex 1.2.16.

  • JTSK03 for a variant of JTSK. Supported since Survex 1.2.16.

  • LONG-LAT for longitude/latitude. The WGS84 datum is assumed. NB *fix expects the coordinates in the order x,y,z which means longitude (i.e. E/W), then latitude (i.e. N/S), then altitude. Supported since Survex 1.2.15.

  • OSGB: followed by a two letter code for the UK Ordnance Survey National Grid. The first letter should be ‘H’, ‘N’, ‘O’, ‘S’ or ‘T’; the second any letter except ‘I’. For example, OSGB:SD. Supported since Survex 1.2.15.

  • S-MERC for the “Web Mercator” spherical mercator projection, used by online map sites like OpenStreetMap, Google maps, Bing maps, etc. Supported since Survex 1.2.15.

  • UTM followed by a zone number (1-60), optionally followed by “N” or “S” specifying the hemisphere (default is North). The WGS84 datum is assumed. A potential source of confusion here is the Military Grid Reference System which divides each UTM zone into latitude bands represented by a letter suffix, so here 33S and 33N have different meanings to those in Survex - they are both parts of UTM zone 33, but both are in the Northern hemisphere (33S is around Sicily, 33N around Cameroon). To use such coordinates in Survex, replace suffixes “C” to “M” with “S”, and “N” to “X” with “N”.

By default, Survex works in an unspecified coordinate system (and this was the only option before *cs was added). However, it’s useful for the coordinate system which the processed survey data is in to be specified if you want to use the processed data in ways which required knowing the coordinate system (such as exporting a list of entrances for use in a GPS). You can now do this by using *cs out.

It is also useful to be able to take coordinates for fixed points in whatever coordinate system you receive them in and put them directly into Survex, rather than having to convert with an external tool. For example, you may have your GPS set to show coordinates in UTM with the WGS84 datum, even though you want the processed data to be in some local coordinate system. Someone else may provide GPS coordinates in yet another coordinate system. You just need to set the appropriate coordinate system with *cs before each group of *fix commands in a particular coordinate system.

If you’re going to make use of *cs, then a coordinate system must be specified for everything, so a coordinate system must be in effect for all *fix commands, and you must set the output coordinate system before any points are fixed.

Also, if *cs is in use, then you can’t omit the coordinates in a *fix command, and a fixed point won’t be invented if none exists.

If you use *cs out more than once, the second and subsequent commands are silently ignored - this makes it possible to combine two datasets with different *cs out settings without having to modify either of them.

Something to be aware of with *cs is that altitudes are currently assumed to be “height above the ellipsoid”, whereas GPS units typically give you “height above sea level”, or more accurately “height above a particular geoid”. This is something we’re looking at how best to address, but you shouldn’t need to worry about it if your fixed points are in the same coordinate system as your output, or if they all use the same ellipsoid. For a more detailed discussion of this, please see: http://expo.survex.com/handbook/survey/coord.htm

See Also

*fix

DATA

Syntax

*data <style> <ordering>

*data

*data default

*data ignore

Example
*data normal from to compass tape clino

*data normal station ignoreall newline compass tape clino
Description
<style>

NORMAL|DIVING|CARTESIAN|TOPOFIL|CYLPOLAR|NOSURVEY|PASSAGE

<ordering>

ordered list of instruments - which are valid depends on the style.

In Survex 1.0.2 and later, TOPOFIL is simply a synonym for NORMAL, left in to allow older data to be processed without modification. Use the name NORMAL by preference.

Most of the styles support two variants - interleaved and non-interleaved. Non-interleaved is “one line per leg”, interleaved has a line for the data shared between two legs (e.g. STATION:FROM/TO, DEPTH:FROMDEPTH/TODEPTH, COUNT:FROMCOUNT/TOCOUNT). Note that not all readings that can be shared have to be, for example here the to/from station name is shared but the depth gauge readings aren’t:

*data diving station newline fromdepth compass tape todepth

In addition, interleaved data can have a DIRECTION reading, which can be F for a foresight or B for a backsight (meaning the direction of the leg is reversed).

In interleaved data, a blank line (one which contains only characters which are set as BLANK) ends the current traverse so can be used to handle branches in the survey, e.g.:

*data normal station newline tape compass clino

1
    9.34   087   -05
2
    ; single leg up unexplored side passage
    4.30   002    +06
3

2
    ; and back to the main package
    6.29   093    -02
4

In data styles which include a TAPE reading (i.e. NORMAL, DIVING, and CYLPOLAR data styles), TAPE may be replaced by FROMCOUNT/TOCOUNT (or COUNT in interleaved data) to allow processing of surveys performed with a Topofil instead of a tape.

In Survex 1.2.44 and later, you can use *data without any arguments to keep the currently set data style, but resetting any state. This is useful when you’re entering passage tubes with branches - see the description of the PASSAGE style below. (This feature was originally added in 1.2.31, but was buggy until 1.2.44 - any data up to the next *data gets quietly ignored.)

DEFAULT

Select the default data style and ordering (NORMAL style, ordering: from to tape compass clino).

IGNORE

Ignores survey data until another *data command sets a different style, or until the end of the enclosing *begin…*end block. Note that commands are still processed, only survey data is ignored. This is useful if you have some survey data which has been superseded by a better survey of the same passage, but you want to keep the superseded data around, just not process it. Added in Survex 1.4.11.

NORMAL

The usual tape/compass/clino centreline survey. For non-interleaved data the allowed readings are: FROM TO TAPE COMPASS CLINO BACKTAPE BACKCOMPASS BACKCLINO; for interleaved data the allowed readings are: STATION DIRECTION TAPE COMPASS CLINO BACKTAPE BACKCOMPASS BACKCLINO.

BACKTAPE was added in Survex 1.2.25.

The CLINO/BACKCLINO reading is not required - if it is omitted in the *data command then the vertical standard deviation is taken to be proportional to the tape measurement for all reading. Alternatively, if the reading is included in the *data command then individual clino readings can be given as OMIT (default -) and will be treated in this way, which allows for data where only some clino readings are missing.

Examples of style NORMAL:

*data normal from to compass clino tape
1 2 172 -03 12.61
2 3 202  -   8.59 ; clino not recorded

*data normal station newline direction tape compass clino
1
  F 12.61 172 -03
2

*data normal from to compass clino fromcount tocount
1 2 172 -03 11532 11873

*data normal station count newline direction compass clino
1 11532
  F 172 -03
2 11873
DIVING

An underwater survey where the vertical information is from a diver’s depth gauge. This style can also be also used for an above-water survey where the altitude is measured with an altimeter. DEPTH is defined as the altitude (Z) so increases upwards by default. So for a diver’s depth gauge, you’ll need to use *CALIBRATE with a negative scale factor (e.g. *calibrate depth 0 -1).

For non-interleaved data the allowed readings are: FROM TO TAPE COMPASS CLINO BACKTAPE BACKCOMPASS BACKCLINO FROMDEPTH TODEPTH DEPTHCHANGE (the vertical can be given as readings at each station, (FROMDEPTH/TODEPTH) or as a change along the leg (DEPTHCHANGE)).

BACKTAPE was added in Survex 1.2.25.

For interleaved data the allowed readings are: STATION DIRECTION TAPE COMPASS BACKTAPE BACKCOMPASS DEPTH DEPTHCHANGE. The vertical change can be given as a reading at the station (DEPTH) or as a change along the leg (DEPTHCHANGE):

*data diving from to tape compass fromdepth todepth
1 2 14.7 250 -20.7 -22.4

*data diving station depth newline tape compass
1 -20.7
 14.7 250
2 -22.4

*data diving from to tape compass depthchange
1 2 14.7 250 -1.7

Survex 1.2.20 and later allow an optional CLINO and/or BACKCLINO reading in DIVING style. At present these extra readings are checked for syntactic validity, but are otherwise ignored. The intention is that a future version will check them against the other readings to flag up likely blunders, and average with the slope data from the depth gauge and tape reading.

CARTESIAN

Cartesian data style allows you to specify the (x,y,z) changes between stations. It’s useful for digitising surveys where the original survey data has been lost and all that’s available is a drawn up version.

*data cartesian from to northing easting altitude
1 2 16.1 20.4 8.7

*data cartesian station newline northing easting altitude
1
  16.1 20.4 8.7
2

By default, the North used is True North, but you can specify to use Magnetic or Grid North (in the input coordinate system) with the *cartesian command, and also specify an additional rotation to apply (since Survex 1.4.10).

In Survex < 1.4.10, if *cs was used then cartesian data were incorrectly interpreted as relative to Grid North in the output coordinate system (if *cs is not used then Grid North in the default unspecified coordinate system is the same as True North).

CYLPOLAR

A CYLPOLAR style survey is very similar to a diving survey, except that the tape is always measured horizontally rather than along the slope of the leg.

*data cylpolar from to tape compass fromdepth todepth
1 2 9.45 311 -13.3 -19.0

*data cylpolar station depth newline tape compass
1 -13.3
 9.45 311
2 -19.0

*data cylpolar from to tape compass depthchange
1 2 9.45 311 -5.7
NOSURVEY

A NOSURVEY survey doesn’t have any measurements - it merely indicates that there is line of sight between the pairs of stations.

*data nosurvey from to
1 7
5 7
9 11

*data nosurvey station
1
7
5

*data
9
11
PASSAGE

This survey style defines a 3D “tube” modelling a passage in the cave. The tube joins the survey stations listed in the order listed. It’s permitted to go between survey stations which aren’t directly linked by the centre-line survey. This can be useful - sometimes the centreline will step sideways or up/down to allow a better sight for the next leg and you can ignore the extra station. You can also define tubes along unsurveyed passages, akin to “nosurvey” legs in the centreline data.

This means that you need to split off side passages into separate tubes, and hence separate sections of passage data, starting with a new *data command with no arguments.

Simple example of how to use this data style (note the use of ignoreall to allow a free-form text description to be given):

*data passage station left right up down ignoreall
1  0.1 2.3 8.0 1.4  Sticking out point on left wall
2  0.0 1.9 9.0 0.5  Point on left wall
3  1.0 0.7 9.0 0.8  Highest point of boulder

Each *data passage data block describes a single continuous tube - to break a tube or to enter a side passage you need to have a second block. With Survex 1.2.30 and older, you had to repeat the entire *data passage line to start a new tube, but in Survex 1.2.31 and later, you can just use *data without any arguments.

For example here the main passage is 1-2-3 and a side passage is 2-4:

*data passage station left right up down ignoreall
1  0.1 2.3 8.0 1.4  Sticking out point on left wall
2  0.0 1.9 9.0 0.5  Point on left wall opposite side passage
3  1.0 0.7 9.0 0.8  Highest point of boulder

; If you need to be compatible with Survex 1.2.30 or earlier
; you need to repeat the full "*data" command here instead.
*data
2  0.3 0.2 9.0 0.5
4  0.0 0.5 6.5 1.5  Fossil on left wall

IGNORE skips a field (it may be used any number of times), and IGNOREALL may be used last to ignore the rest of the data line.

LENGTH is a synonym for TAPE; BEARING for COMPASS; GRADIENT for CLINO; COUNT for COUNTER.

The units of each quantity may be set with the *units command.

See Also

*units

DATE

Syntax

*date <date>

*date <date1>-<date2>

Example
*date 2001

*date 2000.10

*date 1987.07.27

*date 1985.08.12-1985.08.13
Validity

valid at the start of a *begin/*end block.

Description

*date specifies the date that the survey was done. A range of dates can be specified (useful for overnight or multi-day surveying trips).

Dates must be in the order year then month then day, the day or month and day can be omitted. The separator between components must be ..

Dates with just a year (e.g. 2001) are treated as being in the middle of that year. Dates with a month and year (e.g. 2000.10) are treated as being in the middle of that month.

See Also

*begin, *instrument, *team

DECLINATION

Syntax

*declination auto <x> <y> <z>

*declination <declination> <units>

Description

The *declination command is the modern way to specify magnetic declinations in Survex. Magnetic declination is the difference between Magnetic North and True North. It varies over time as the Earth’s magnetic field moves, and also with location. Compass bearings are measured relative to Magnetic North - adding the magnetic declination gives bearings relative to True North.

Prior to 1.2.22, *calibrate declination was used instead. If you use a mixture of *calibrate declination and *declination, they interact in the natural way - whichever was set most recently is used for each compass reading (taking into account survey scope). We don’t generally recommend mixing the two, but it’s useful to understand how they interact if you want to combine datasets using the old and new commands, and perhaps if you have a large existing dataset and want to migrate it without having to change everything at once.

Note that the value specified uses the conventional sign for magnetic declination, unlike the old *calibrate declination which needed a value with the opposite sign (because *calibrate specifies a zero error), so take care when updating old data, or if you’re used to the semantics of *calibrate declination.

If you have specified the output coordinate system (using *cs out) then you can use *declination auto (and we recommend that you do). This is supported since Survex 1.2.21 and automatically calculates magnetic declinations based on the IGRF (International Geomagnetic Reference Field) model. A revised version of the IGRF model is usually issued every 5 years, and calculates values using a model based on observations for years before it is issued, and on predictions for 5 years after it is issued. Survex 1.2.43 updated to using version 13 in early 2020.

The IGRF model takes a date and a location as inputs. Survex uses the specified date of the survey, and uses the “x y z” coordinates specified in the *declination auto command as the location in the current input coordinate system (as set by *cs). Most users can just specify a single representative location somewhere in the area of the cave. If you’re not sure what to use pick some coordinates roughly in the middle of the bounding box of the cave - it doesn’t need to be a fixed point or a known refindable location, though it can be if you prefer.

Survex 1.2.27 and later also automatically correct for grid convergence (the difference between Grid North and True North) when *declination auto is in use, based on the same specified representative location.

You might wonder why Survex needs a representative location instead of calculating the magnetic declination and grid convergence for the actual position of each survey station. The reason is that we need to adjust the compass bearings before we can solve the network to find survey station locations. Both magnetic declination and grid convergence don’t generally vary significantly over the area of a typical cave system - if you are mapping a very large cave system, or caves over a wide area, or are working close to a magnetic pole or where the output coordinate system is rather distorted, then you can specify *declination auto several times with different representative locations for different areas of the cave system - the one currently in effect is used for each survey leg.

For each *declination auto command cavern will (since Survex 1.4.2) report the range of calculated declination values and the dates at which the ends of the range were obtained, and also the grid convergence (which doesn’t vary with time). This appears in the log - if you processed the data with aven you can view this by using “File->View Log”. It looks like this:

1623.svx:20: info: Declination: -0.4° @ 1977-07-02 / 3.8° @ 2018-07-21, grid convergence: -0.9°
 *declination auto 36670.37 83317.43 1903.97

Generally it’s best to specify a suitable output coordinate system, and use *declination auto so Survex corrects for magnetic declination and grid convergence for you. Then Aven knows how to translate coordinates to allow export to formats such as GPX and KML, and to overlay terrain data and other geodata.

If you don’t specify an output coordinate system, but fix one or more points then Survex works implicitly in the coordinate system your fixed points were specified in. This mode of operation is provided for compatibility with datasets from before support for explicit coordinate systems was added to Survex - it’s much better to specify the output coordinate system as above. But if you have a survey of a cave which isn’t connected to any known fixed points then you’ll need to handle it this way, either fixing an entrance to some arbitrary coordinates (probably (0,0,0)) or letting Survex pick a station as the origin. If the survey was all done in a short enough period of time that the magnetic declination won’t have changed significantly, you can just ignore it and Grid North in the implicit coordinate system will be Magnetic North at the time of the survey. If you want to correct for magnetic declination, you can’t use *declination auto because the IGRF model needs the real world coordinates, but you can specify literal declination values for each survey using *declination <declination> <units>. Then Grid North in the implicit coordinate system is True North.

See Also

*calibrate

DEFAULT

Syntax

*default calibrate

*default data

*default units

Description

*default restores defaults for given settings. This command is deprecated - you should instead use: *calibrate default, *data default, *units default.

See Also

*calibrate, *data, *units

END

Syntax

*end <survey>

*end

Validity

valid for closing a block started by *begin in the same file.

Description

Closes a block started by *begin.

See Also

*begin

ENTRANCE

Syntax

*entrance <station>

Example
*entrance P163
Description

*entrance marks a station as an entrance. This information is used by aven to allow entrances to be highlighted.

EQUATE

Syntax

*equate <station> <station>...

Example
*equate chosspot.1 triassic.27
Description

*equate specifies that the station names in the list refer to the same physical survey station. An error is given if there is only one station listed.

See Also

*infer equates

EXPORT

Syntax

*export <station>...

Example
*export 1 6 17
Validity

valid at the start of a *begin/*end block.

Description

*export marks the stations named as referable to from the enclosing survey. To be able to refer to a station from a survey several levels above, it must be exported from each enclosing survey.

See Also

*begin, *infer exports

FIX

Syntax

*fix <station> [reference] <x> <y> <z>

*fix <station> [reference] <x> <y> <z> <std err>

*fix <station> [reference] <x> <y> <z> <horizontal std err> <vertical std err>

*fix <station> [reference] <x> <y> <z> <x std err> <y std err> <z std err>

*fix <station> [reference] <x> <y> <z> <x std err> <y std err> <z std err> <cov(x,y)> <cov(y,z)> <cov(z,x)>

*fix <station>

Example
*fix entrance.0 32768 86723 1760

*fix KT114_96 reference 36670.37 83317.43 1903.97
Description

*fix fixes the position of <station> at the given coordinates. If you haven’t specified the coordinate system with *cs, you can omit the position and it will default to (0,0,0) which provides an easy way to specify a point to arbitrarily fix rather than rely on cavern picking one (which has the downsides of the choice potentially changing when more survey data is added, and of triggering an “info” message).

The standard errors default to zero (fix station exactly). cavern will give an error if you attempt to fix the same survey station twice at different coordinates, or a warning if you fix it twice with matching coordinates.

You can also specify just one standard error (in which case it is assumed equal in X, Y, and Z) or two (in which case the first is taken as the standard error in X and Y, and the second as the standard error in Z).

If you have covariances for the fix, you can also specify these - the order is cov(x,y) cov(y,z) cov(z,x).

If you’ve specified a coordinate system (see *cs) then that determines the meaning of X, Y and Z (if you want to specify the units for altitude, note that using a PROJ string containing +vunits allows this - e.g. +vunits=us-ft for US survey feet). If you don’t specify a coordinate system, then the coordinates must be in metres. The standard deviations must always be in metres (and the covariances in metres squared).

You can fix as many stations as you like - just use a *fix command for each one. Cavern will check that all stations are connected to at least one fixed point so that co-ordinates can be calculated for all stations. If there is unconnected survey data then you’ll get a warning (since Survex 1.4.10; in earlier versions this was an error) and only the connected data is processed.

By default cavern will warn about stations which have been *fix-ed but are not used otherwise, as this might be due to a typo in the station name. Uses in survey data and (since 1.4.9) *entrance count for these purposes. This warning is unhelpful if you want to include a standard file of benchmarks, some of which won’t be used. In this sort of situation, specify reference after the station name in the *fix command to suppress this warning for a particular station. It’s OK to use reference on a station which is used.

Since Survex 1.4.10 it’s an error to specify reference without coordinates (e.g. *fix a reference) as this usage doesn’t really make sense.

Note

X is Easting, Y is Northing, and Z is altitude. This convention was chosen since on a map, the horizontal (X) axis is usually East, and the vertical axis (Y) North. The choice of altitude (rather than depth) for Z is taken from surface maps, and makes for less confusion when dealing with cave systems with more than one entrance. It also gives a right-handed set of axes.

FLAGS

Syntax

*flags <flags>

Example
*flags duplicate not surface
Description

*flags updates the currently set flags. Flags not mentioned retain their previous state. Valid flags are duplicate, splay, and surface, and a flag may be preceded with not to turn it off.

Survey legs marked surface are hidden from plots by default, and not included in cave survey length calculations.

Survey legs marked as duplicate or splay are also not included in cave survey length calculations; legs marked splay are ignored by the extend program. duplicate is intended for the case when if you have two different surveys along the same section of passage (for example to tie two surveys into a permanent survey station); splay is intended for cases such as radial legs in a large chamber, or to walls and other features with a disto-x or similar device.

See Also

*begin

INCLUDE

Syntax

*include <filename>

Example
*include mission

*include "the pits"
Description

*include processes <filename> as if it were inserted at this place in the current file - i.e. the current settings are carried into the included file and any alterations to settings in the included file will be carried back again. There’s one exception to this for historical reasons, which is that the survey prefix is restored upon return to the original file. Since *begin and *end nesting cannot cross files, this can only make a difference if you use the deprecated *prefix command.

If the filename contains spaces, it must be enclosed in double quotes.

An included file which does not have a complete path is resolved relative to the directory which the parent file is in (just as relative HTML links do).

The included file can be any filetype which cavern can process, so you can *include compassdata.mak, *include compassdata.dat, *include wallsdata.wpj or *include wallsdata.srv to allow processing mixed-format datasets.

If the filename as specified is not found, cavern will try adding a .svx extension, and will also try translating \ to /.

INFER

Syntax

*infer plumbs on

*infer plumbs off

*infer equates on

*infer equates off

*infer exports on

*infer exports off

Description

*infer plumbs on tells cavern to interpret gradients of ±90 degrees as UP/DOWN (so it will not apply the clino correction to them). This is useful when you have data which uses this convention for plumbed legs.

*infer equates on tells cavern to interpret a leg with a tape reading of zero as a *equate which this prevents tape corrections being applied to them. This is useful when you have data which uses this convention for equating stations.

*infer exports on is necessary when you have a dataset which is partly annotated with *export. It tells cavern not to complain about missing *export commands in the parts of the dataset it is enabled for. Also stations which were used to join surveys are marked as exported in the 3d file.

INSTRUMENT

Syntax

*instrument <instrument> <identifier>

Example
*instrument compass "CUCC 2"
*instrument clino "CUCC 2"
*instrument tape "CUCC Fisco Ranger open reel"
Validity

valid at the start of a *begin/*end block.

Description

*instrument specifies the particular instruments used to perform a survey.

See Also

*begin, *date, *team

PREFIX

Syntax

*prefix <survey>

Example
*prefix flapjack
Description

*prefix sets the current survey.

Caveats

*prefix is deprecated - you should use *begin and *end instead.

See Also

*begin, *end

REF

Syntax

*ref <string>

Example
*ref "survey folder 2007#12"
Validity

valid at the start of a *begin/*end block.

Description

*ref allows you to specify a reference. If the reference contains spaces, you must enclose it in double quotes. Survex doesn’t try to interpret the reference in any way, so it’s up to you how you use it - for example it could specify where the original survey notes can be found.

*ref was added in Survex 1.2.23.

See Also

*begin, *date, *instrument, *team

REQUIRE

Syntax

*require <version>

Example
   *require 1.2.14 ; for *cs

::

   *require 1.4 ; equivalent to 1.4.0

::

   *require 1 ; equivalent to 1.0.0
Description

*require checks that the version of cavern in use is at least <version> and stops with an error if not.

If your dataset requires a feature introduced in a particular version, you can add a *require command and users will know what version they need to upgrade to, rather than getting an error message and having to guess what the real problem is. We suggest noting the reason for the requirement in a comment after the *require command, like in the first example above.

SD

Syntax

*sd <quantity list> <standard deviation> <units>

Example
*sd tape 0.15 metres

*sd compass backcompass clino backclino 0.5 degrees
Description

*sd specifies the standard deviation of a measurement.

<quantity> is one of (each group gives alternative names for the same quantity):

  • TAPE, LENGTH

  • BACKTAPE, BACKLENGTH (added in Survex 1.2.25)

  • COMPASS, BEARING

  • BACKCOMPASS, BACKBEARING

  • CLINO, GRADIENT

  • BACKCLINO, BACKGRADIENT

  • COUNTER, COUNT

  • DEPTH

  • DECLINATION

  • DX, EASTING

  • DY, NORTHING

  • DZ, ALTITUDE

  • LEFT

  • RIGHT

  • UP, CEILING

  • DOWN, FLOOR

  • LEVEL

  • PLUMB

  • POSITION

<standard deviation> is a positive real number, e.g. 0.05.

<units> specifies the units, which must be appropriate for the quantity or quantities in the list (e.g. metres for distance, degrees for an angle). See *units below for full list of valid units.

To utilise this command fully you need to understand what a standard deviation is. It gives a value to the ‘spread’ of the errors in a measurement. Assuming that these are normally distributed we can say that 95.44% of the actual lengths will fall within two standard deviations of the measured length, e.g. a tape SD of 0.25 metres means that the actual length of a tape measurement is within ±0.5 metres of the recorded value 95.44% of the time. So if the measurement is 7.34m then the actual length is very likely to be between 6.84m and 7.84m. This example corresponds to BCRA grade 3. Note that this is just one interpretation of the BCRA standard, taking the permitted error values as 2SD 95.44% confidence limits. If you want to take the readings as being some other limit (e.g. 1SD = 68.26%) then you will need to change the BCRA3 and BCRA5 files accordingly. This issue is explored in more detail in various surveying articles.

See Also

*units

SET

Syntax

*set <item> <character list>

Example
*set blank x09x20
*set decimal ,

This example sets the decimal separator to be a comma. Note that here we need to eliminate comma from being a blank before setting it as a decimal - otherwise the comma in *set decimal , is parsed as a blank, and cavern sets decimal to not have any characters representing it.

Here’s an example of how to allow additional characters in station names:

*set names ?+_

After this ?, + and _ will be allowed in names (in addition to characters A-Z, a-z and 0-9 which are always allowed). *set replaces the previous setting so while _ and - are both allowed by default, - no longer is after this command because it isn’t in the list.

Description

*set sets the specified <item> to the character or characters given in <character list>.

The characters specified in <character list> may not be alphanumeric since these characters are used for station names and for readings.

In <character list>, x followed by two hex digits means the character with that hex value, e.g. x20 is a space.

The complete list of items that can be set, the defaults (in brackets), and the meaning of the item, is:

BLANK (x09x20,)

Separates fields

COMMENT (;)

The rest of the current line is a comment

DECIMAL (.)

Decimal point character

EOL (x0Ax0D)

End of line character

KEYWORD (*)

Introduces keywords

MINUS (-)

Indicates negative number

NAMES (_-)

Non-alphanumeric chars permitted in station names (letters and numbers are always permitted).

OMIT (-)

Contents of field omitted (e.g. in plumbed legs)

PLUS (+)

Indicates positive number

ROOT (\)

Prefix in force at start of current file (use of ROOT is deprecated)

SEPARATOR (.)

Level separator in prefix hierarchy

SOLVE

Syntax

*solve

Example
*include 1997data
*solve
*include 1998data
Description

*solve distributes misclosures around any loops in the survey (in the same way that happens implicitly after reading all the data), then fixes the positions of all existing stations.

This command is intended for situations where you have some new surveys adding extensions to an already drawn-up survey which you wish to avoid completely redrawing. You can read in the old data, use *solve to fix it, and then read in the new data. Then old stations will be in the same positions as they are in the existing drawn up survey, even if new loops have been formed by the extensions.

TEAM

Syntax

*team <person> [<role>...]

Example
*team "Nick Proctor" compass clino tape
*team "Anthony Day" notes pictures tape
Validity

valid at the start of a *begin/*end block.

Description

*team specifies the people involved in a survey and optionally what role or roles they filled during that trip. Unless the person is only identified by one name you need to put double quotes around their name.

See Also

*begin, *date, *instrument

TITLE

Syntax

*title <title>

Example
*title Dreamtime

*title "Mission Impossible"
Description

*title allows you to set a descriptive title for a survey. If the title contains spaces, you need to enclose it in double quotes (“”). If there is no *title command, the title defaults to the survey name given in the *begin command.

TRUNCATE

Syntax

*truncate <length>

*truncate off

Description

Station names may be of any length in Survex, but some other (mostly older) cave surveying software only regards the first few characters of a name as significant (e.g. “entran” and “entrance” might be treated as the same). To facilitate using data imported from such a package, Survex allows you to truncate names to whatever length you want (but by default truncation is off).

Figures for the number of characters which are significant in various software packages: Compass currently has a limit of 12, CMAP has a limit of 6, Smaps 4 had a limit of 8, Surveyor87/8 used 8. Survex itself used 8 per prefix level up to version 0.41, and 12 per prefix level up to 0.73 (more recent versions removed this rather archaic restriction).

See Also

*case

UNITS

Syntax

*units <quantity list> [<factor>] <unit>

*units default

Example
*units tape metres

*units compass backcompass clino backclino grads

*units dx dy dz 1000 metres ; data given as kilometres

*units left right up down feet
Description

*units changes the current units of all the quantities listed to [<factor>] <unit>. Note that quantities can be expressed either as the instrument (e.g. COMPASS) or the measurement (e.g. BEARING).

<quantity> is one of the following (grouped entries are just alternative names for the same thing):

  • TAPE/LENGTH

  • BACKTAPE/BACKLENGTH (added in Survex 1.2.25)

  • COMPASS/BEARING

  • BACKCOMPASS/BACKBEARING

  • CLINO/GRADIENT

  • BACKCLINO/BACKGRADIENT

  • COUNTER/COUNT

  • DEPTH

  • DECLINATION

  • DX/EASTING

  • DY/NORTHING

  • DZ/ALTITUDE

  • LEFT

  • RIGHT

  • UP/CEILING

  • DOWN/FLOOR

<factor> allows you to easy specify situations such as measuring distance with a diving line knotted every 10cm (*units distance 0.1 metres). If <factor> is omitted it defaults to 1.0. If specified, it must be non-zero.

Valid units for listed quantities are:

TAPE/LENGTH, BACKTAPE/BACKLENGTH, COUNTER/COUNT, DEPTH, DX/EASTING, DY/NORTHING, DZ/ALTITUDE in YARDS|FEET|METRIC|METRES|METERS (default: METRES)

CLINO/GRADIENT, BACKCLINO/BACKGRADIENT in DEGS|DEGREES|GRADS|MINUTES|PERCENT|PERCENTAGE (default: DEGREES)

COMPASS/BEARING, BACKCOMPASS/BACKBEARING, DECLINATION in DEGS|DEGREES|GRADS|MINUTES|QUADS|QUADRANTS (default: DEGREES)

FEET and YARDS use the international definition of a foot (exactly 0.3048m). If you want to use a different definition, you can specify it explicitly - for example, for the US survey foot:

*units tape 0.3048006096012192 meters ; US survey foot

or for the Indian survey foot:

*units tape 0.3047996 meters ; Indian survey foot

QUADRANTS are a style of bearing used predominantly in land survey, and occasionally in survey with handheld instruments. All bearings are N or S, a numeric from 0 to 90, followed by E or W. For example S34E to refer to 146 degrees, or 34 degrees in the SE quadrant. In this format, exact cardinal directions may be simply alphabetic. E.g. N is equivalent to N0E and E is equivalent to N90E. This unit was added in Survex 1.2.44.

GRADS are an angle unit where 400 grads = 360 degrees. They’re also known as “neugrads” (or sometimes “gons”).

Survex has long supported MILS as an alias for GRADS. However, this seems to be a bogus definition of a “mil” which is unique to Survex (except that Therion has since copied it) - there are several different definitions of a “mil” but they vary from 6000 to 6400 in a full circle, not 400. Because of this we deprecated MILS in Survex 1.2.38 - you can still process data which uses them but you’ll now get a warning, and we recommend you update your data.

For example, if your data uses

*units compass mils

then you need to determine what the intended units actually are. If there are 400 in a full circle, then instead use this (which will work with older Survex versions too):

*units compass grads

If the units are actually mils, you can specify that in terms of degrees. For example, there are 6400 NATO mils in a full circle, so one NATO mil is 360/6400 degrees, and 360/6400=0.05625 so you can use this (which also works with older Survex versions):

; Compass readings are NATO mils (6400 = 360 degrees)
*units compass 0.05625 degrees
See Also

*calibrate