Bob Thrun’s CMAP

Survex can read CMAP processed survey data, commonly known as CMAP XYZ files. CMAP no longer seems to be used, but we’ve kept the support in place so it’s there if anyone finds old data and wants to view it.

Support was added long ago (Survex 1.0.4) but you really want to use Survex 1.4.9 or later due to a feet to metres conversion bug in all versions before this, which scaled all returned coordinates from CMAP XYZ files by a factor of about 10.76.

CMAP XYZ files contain a timestamp. CMAP was originally written for computers where the clock was just set to localtime so it seems likely this timestamp is in localtime, but it does not specify a timezone. Survex assumes it’s in UTC, which is at least fairly central in the possibilities, but may mean timestamps are off by up to about half a day. The timestamps in example files all use two digit years. It’s not documented how CMAP handles years 2000 and later, so we assume 4 digit years are correct, years < 50 are 20xx, and other years get 1900 added to them (so year 101 is 2001).

CMAP XYZ files don’t seem to contain any station flags. There’s a single character “type” which acts as a leg flag of sorts, but it seems the meaning is up to the user so we don’t try to interpret it. We assume all the data is underground (so all stations get the “underground” flag).

There are two variants of CMAP XYZ files. CMAP v16 and later produce the “shot” variant (with extension .sht), which is well supported by Survex.

Older CMAP versions produced the “station” variant (with extension .adj for adjusted data and .una for unadjusted data). Survex only supports reading stations from these - the survey legs linking them are currently ignored.