Questions about Walls survey software

[rchrds]

Forrest, you have to catch me by email, I don't always look here. Jon has helped you on most of this, but let me recap on something, re the datum.

Datum is established in Walls in your Project Properties, Geographical Reference tab. In fact, this is just about all this tab does, as though it asks for a complete location, the location you enter here has no bearing, aside from the program using the datum you enter here as the reference datum for the entire project. Each of your locations are entered later in the manner that I sent you, and Jon explained here. If you are going to use locations in NAD27 from your GPS set to NAD27, ensure that on Geographical Reference tab, the Datum: reads NAD27 CONUS, as the picture below shows.

Jon has it correct, you MUST use a new #units statement for your georeferences, but let me explain why.

As he said, all of your unit formats that you see in a GPS are meters based. This is a convention based on every other graphical information system (GIS) program out there, which are all meters based, at their core. In fact, latitude and longitude are meters based, as calculations used to create the angular relations that delineate latitude and longitude are done in meters. UTM is also meters.

So, you might think, that hey, I survey in meters (Mexico) so I am good.

Not so, Charlie Brown.

The other critical part of the units statement is the "order" component.

A unit statement used for survey typically looks like this:

#units=meters order=DAV ;(dry cave) D is for distance, A is for azimuth, V is for vertical angle
#units=feet order=DA Tape=SS ;(underwater) D is for Distance, A is for azimuth, the tape is broken into station to station method

but a georeference units statement looks like this:

#units=meters order=ENU ;this is unique- E is east, N is north, U is up or elevation.

There are times in which you might need to have the units for a georeference be set to feet, like if you live on your own planet that was surveyed in feet, just to be difficult, but in all other cases, it will be meters. The order can be arranged how you like it- it doesn't have to be ENU, and in a case where you had a hundred reference locations for different caves within the same project and you were manually entering the data, and perhaps your northing is in the first column and easting in your second column of your excel file you were reading from- in this case, you might want to make the order NEU, just to make it easier to type.

When compiling, the other thing you need to watch out for:

Typically, in the us, you are going to want to see your length results in feet, so on your Project Properties General tab, you will have your Review Units set to Feet. When you review, all of the numbers in the segments tab will be in feet. (lots of caveats to that length number, read the help file.) However, once you start dealing with georeferences, it is a good habit to set your units in the General tab to meters- yes, this will change your length on the Segments tab to meters, however any other function in the Details/Rpts... button will show up in meters, which is what you have to have to export a shapefile, or show your list of station locations using the Coordinates... button.

More later, I have to go to work- Forrest, I will be back and happy to teach either or both an underwater survey and a Walls class at the CDS convention this year. Perhaps Jon and I can team up on them.

Jason

[rchrds]

Here is a picture that shows: The Geographical Reference tab on the Project Properties box, set to NAD27 CONUS. Also shown, the Details/Reports... window with the project set to meters (see Units: Meters at the top) and the two buttons that export shapefiles, and export the coordinate list.

Jason