General: How do I? — Survex 1.4.21 documentation

# General: How do I?

## Create a new survey

You create a text file containing the relevant survey data, using a text editor, and save it with a suitable name with a `.svx` extension. The easiest way is to look at some of the example data and use that as a template. Nearly all surveys will need a bit of basic info as well as the survey data itself: e.g. the date (`*date`), comments about where, what cave, a name for the survey (using `*begin` and `*end`), instrument error corrections, etc. Here is a typical survey file:

All the lines starting with `;` are comments, which are ignored by Survex. You can also see the use of `DOWN` for plumbs, and `*calibrate tape` for dealing with a tape length error (in this case the end of the tape had fallen off so measurements were made from the 20cm point).

    *equate chaos.1 triassic.pt3.8
    *equate chaos.2 triassic.pt3.9

    *begin chaos
    *title "Bottomless Pit of Eternal Chaos to Redemption pitch"
    *date 1996.07.11
    *team "Nick Proctor" compass clino tape
    *team "Anthony Day" notes pictures tape
    *instrument compass "CUCC 2"
    *instrument clino "CUCC 2"
    ;Calibration: Cairn-Rock 071 072 071,  -22 -22 -22
    ;       Rock-Cairn 252 251 252,  +21 +21 +21
    ;Calibration at 161d entrance from cairn near entrance to
    ;prominent rock edge lower down. This is different from
    ;calibration used for thighs survey of 5 July 1996

    *export 1 2

    ;Tape is 20cm too short
    *calibrate tape +0.2

    1 2 9.48 208 +08
    2 3 9.30 179 -23
    3 4 2.17 057 +09
    5 4 10.13 263 +78
    5 6 2.10 171 -73
    7 6 7.93 291 +75
    *begin
    *calibrate tape 0
    8 7 35.64 262 +86 ;true length measured for this leg
    *end
    8 9 24.90 - DOWN
    10 9 8.61 031 -43
    10 11 2.53 008 -34
    11 12 2.70 286 -20
    13 12 5.36 135 +23
    14 13 1.52 119 -12
    15 14 2.00 036 +13
    16 15 2.10 103 +12
    17 16 1.40 068 -07
    17 18 1.53 285 -42
    19 18 5.20 057 -36
    19 20 2.41 161 -67
    20 21 27.47 - DOWN
    21 22 9.30 192 -29
    *end chaos

## Organise my surveys

This is actually a large subject. There are many ways you can organise your data using Survex. Take a look at the example dataset for some ideas of ways to go about it.

### Fixed Points (Control Points)

The `*fix` command is used to specify fixed points (also know as control points). See the description of this command in the “Cavern Commands” section of this manual.

### More than one survey per trip

Suppose you have two separate bits of surveying which were done on the same trip. So the calibration details, etc. are the same for both, but you want to give a different survey name to the two sections. This is easily achieved like so:

    *begin
    *calibrate compass 1.0
    *calibrate clino 0.5
    *begin altroute
    ; first survey
    *end altroute
    *begin faraway
    ; second survey
    *end faraway
    *end

## Add surface topography

Survex 1.2.18 added support for loading terrain data and rendering it as a transparent surface. Currently the main documentation for this is maintained as a wiki page as this allows us to update it between releases.

This supports loading data in the HGT format that NASA offers SRTM data in. The SRTM data provides terrain data on a 1 arc-second grid (approximately 30m) for most of the world.

## Overlay a grid

Aven is able to display a grid, but this functionality isn’t currently available in printouts. You can achieve a similar effect for now by creating a `.svx` file where the survey legs form a grid.

If you want to do this, we suggest fixing points at the end of each grid line and using the `NOSURVEY` data style to add effectively elastic legs between these fixed points. This is simpler to generate than generating fake tape/compass/clino legs and is very fast for cavern to process. Some tips for doing this

Here’s a small example of a 500mx500m grid with lines 100m apart:

    *fix 0W 000 000 0
    *fix 1W 000 100 0
    *fix 2W 000 200 0
    *fix 3W 000 300 0
    *fix 4W 000 400 0
    *fix 5W 000 500 0

    *fix 0E 500 000 0
    *fix 1E 500 100 0
    *fix 2E 500 200 0
    *fix 3E 500 300 0
    *fix 4E 500 400 0
    *fix 5E 500 500 0

    *fix 0S 000 000 0
    *fix 1S 100 000 0
    *fix 2S 200 000 0
    *fix 3S 300 000 0
    *fix 4S 400 000 0
    *fix 5S 500 000 0

    *fix 0N 000 500 0
    *fix 1N 100 500 0
    *fix 2N 200 500 0
    *fix 3N 300 500 0
    *fix 4N 400 500 0
    *fix 5N 500 500 0

    *data nosurvey from to

    0W 0E
    1W 1E
    2W 2E
    3W 3E
    4W 4E
    5W 5E

    0S 0N
    1S 1N
    2S 2N
    3S 3N
    4S 4N
    5S 5N

## Import data from other programs

Survex supports a number of features to help with importing existing data.

Unprocessed survey data in Compass or Walls format can be processed directly, and mixed datasets are support to aid combining data from different projects using different software. This also can help if you want to migrate data into Survex from another format as you can leave the existing data in its original format and just use Survex native format for new data, or if you prefer to convert everything to Survex native format it can be done in phases.

Processed survey data in Compass or CMAP formats can be viewed in `aven` and used with any Survex command line tool which takes processed survey data.

For data in formats without explicit support, you may be able to read the data by renaming the file to have a `.svx` extension and adding a few Survex commands at the start of the file to set things up so Survex can read the data which follows. For example, you can specify the ordering of items on a line using `*data` (see Survex Keywords above), and you can specify the characters used to mean different things using `*set` (see Survex Keywords above).

The `ignore` and `ignoreall` items in the `*data` command are often particularly useful, e.g. if you have a dataset with LRUD info or comments on the ends of lines.

## See errors and warnings that have gone off the screen

When you run Survex it will process the specified survey data files in order, reporting any warnings and errors. If there are no errors, the output files are written and various statistics about the survey are displayed. If there are a lot of warnings or errors, they can scroll off the screen and it’s not always possible to scroll back to read them.

The easiest way to see all the text is to use `cavern --log` to redirect output to a `.log` file, which you can then inspect with a text editor.

## Create an Extended Elevation

You can create a simple extended elevation from `aven`, using the `File->Extended Elevation...` menu option. This takes the currently loaded survey file and “flattens” it.

Behind the scenes this runs the `extend` command-line program. This program offers more powerful features, such as being able to control which way legs are folded and where loops are broken, but currently these features are only accessible from the command line (the intention is to allow them to be used from `aven` in the future).