General surveying questions

[jlillest]

We might need to see what software we want to use for this system, I would assume that we soon will need several people entering data. I looked at a couple other ones
I downloaded therion and wanted to play around a little
http://therion.speleo.sk/download.php
what else is out there and really worth to focus on
walls, compass, wincarst, arianes, onstation ......
FW should we look into the capabilities of other software?

It should be noted that Therion is a map drawing program and does not crunch data by itself. Therion crunches data externally through cave survey programs like Survex. Survex is another nice program, but more complex than Walls & Compass without the nice map display features. If you're a programmer you should be able to pick up on Survex fairly quick as it's entirely non-GUI based.

The really neat thing about Compass is its ability to export kml files that you can view in Google Earth. That way you can share with your fellow explorers the map overlaid on terrain as it develops. The kml files are just text and can be easily edited. For me that is the killer feature that Compass has over the others. Essentially they do much the same thing, with greater or lesser amounts of bugginess and varying user interfaces. If it could output kml files directly I would probably switch to Walls.

I'm not worried about exporting to kml as I can do better maps with GIS applications, still share shapefiles and data and not have to worry about Google making my private data available to everyone without my knowledge (which they've done once or twice).

-Jon

[FW]

Lets see, Fords are better than Chevrolets, unless you try to integrate GPS from the passenger seat? So far, I like Walls better that anything else I have seen, but I admit other survey programs have some nice features.

[rchrds]

1. Do you start numbering on the surface?
2. Do you start with station 0, 1, or something different (like A1)?
3. If you are working on a multi-entrance cave (like Peacock) and have what you thought were two different caves that end up connecting, how do you tie them together, especially if they don't have unique station numbers?

You probably noticed I have started using Walls software, but I suspect any other software would have the same type issues.

1. Yes and No. Yes, your survey has to be tied to the surface. (unless you know of a USGS survey marker that is underwater) No, your numbers do not have to sequentially tie to the surface. Only your survey software has to make that connection. There are two things at work here. The first is how accurately do you wish to locate your entrance? If your survey only consists of underwater survey, with no stations or ability to surface connect further into the cave, than GPS is probably going to be good enough to establish a datum. (Fixed location from which your survey is referenced.) If your cave has 35 miles of passage, and the furthest reaches are 10-12 linear miles from your entrance, GPS is NOT going to be good enough. In either case, you have to have the ability to either get a good GPS fix (i.e. sky not partially obscured by a bluff wall or mountain on one side) or the ability to surface survey to a surveyed reference. (USGS marker or similar.) This will likely require at least one, possibly more shots from the surface of the water out into an open area or to a marker.

Example 1: My short underwater cave, 30 stations, 1 mile of passage. I want to overlay it on Google Earth to see if there are any other nearby entrances. Go ahead and use the GPS. It will get you close enough for what you want.

Example 2: My 37 mile cave has three entrances, and I want to find out which valley to dig in 13 miles away to try to open a fourth entrance. In this case, you will find that for every foot or so of error you have in the GPS position, the end of the passage 13 miles away might swing 100 feet. (Obviously geometry matters here.) In this case, you need to be able to surface survey not only to a minimum error reference station, (preferably the same one your maps are referenced to) but you also need to be able to surface survey between the entrances to close the loop and mitigate error.

2. It doesn't matter. For my first dive or trip into a cave, I always label my GPS station as 0Datum. This is how it is labeled in walls. Then I count up. I might later have to renumber stations if i survey out, and forget, but hey, that is easy. Some pencil and erasor time on the original survey book sheets, and then change them up in Walls. If I know for a fact that there are multiple nearby entrances that might or might not be connected, then I use something more descriptive, like Turtle0, Scary0, etc shortening the name of the cave. However, I only use this for the zero datum stations, the rest of the numbers are generic. This is because I can use the #prefix statement in walls. (later question.) All of these datum stations will eventually be brought together in a single georeference file in walls, so they can be easily managed.

3. If this happens, and you have used generic labels throughout the separate caves, use the #prefix directive (directly from the Walls manual):

--------------------------
If our project area contained many caves connected, for example, by surface surveys or GPS positions, it would be nice if we could compile the complete data set without having to revise the original station names simply to make them globally unique. Also, if we wanted to insure that some arbitrary collection of SRV files is truly self-contained, we would need some way to say whether or not station S1 in file A and station S1 in file B, for example, are physically the same station. To satisfy such requirements, the SRV format provides the following directive for creating qualifying name prefixes:

#Prefix <name>

or

#Prefix

The first form assigns an implied name prefix to all stations following it in the file whose prefix is not explicitly overridden. The second form reassigns the default empty prefix. For example, PEP:A123, BRINCO:A123, and :A123 are station names with explicit prefixes. These stations are assumed to be physically different, although they all could have originally appeared in survey books as simply A123. A colon is used to separate the prefix from the original name portion. (The override :A123 is equivalent to a non-prefixed A123.) Notice that in the Hackberry Cave illustration (see SRV Files - Overview), all stations are assigned prefix "HACK", except for the surface tie-in, SUR:S1.
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Ok, and for some separate points brought up later:

Numbering stations: After dealing with the 37 mile long cave I am currently drafting, I have to agree that the Prefix letter method, exactly as Mike described, has worked quite well. In a manner, it allows you to know where things are in the cave, particularly when they are quite out of hand with maziness. I have seen this used in a number of places in Mexico, and it works well there also. I see Jon's point, and perhaps this might work on a project where the day locations were found might be important (as seems to be with some sorts of projects) However the survey tends to be disjointed, particularly in mazy stuff, and it can be difficult for someone not involved with the project to intuitively find their way around using this method. Keep in mind, that you are limited to 8 characters with walls (not including the #prefix!)

Survey Markers: I also agree with Mike to an extent in this regard. I do not leave station markers except at junctions, important locations (bottle drops) or leads (which will become junctions, or be removed.) There is just no need to leave stations in almost any other circumstance. The only exception would be in a very long passage where your stations might be very difficult to discern due to uniformity of passage depth and shape, and here, you could leave a station. However, as you commented, stations get blown out. This is why it is so important to make stations on permanent locations where possible, and then TAKE A NOTE AT THE STATION when you survey- that way, you can find the station again, regardless of the location of the line. I cannot tell you how important I find this particular piece of information that almost nobody does. It takes only an extra second or two to write <small rock on right> or <floor loop before dome> and with this information and the depth, 90 percent of the time, you can return to the same station again if the line was well placed, as you would likely use it again anyway.

If you have the time and stability to make custom station markers as Mike did in Peacock, then by all means. But I have found that using the line arrows that are rough on the back, along with using a survey pencil that is not too sharp, will allow you to write the survey station on the back (or front) of the marker in the water, and it wont disappear. I have placed survey stations in Jackson Blue that are now 10 years old that I can still read. If your station changes, just write a new one, and take the old one out and scrub it clean for re-use.

Data storage and management:This is one thing that cave divers to badly. Writing your survey data on a slate, copying it down into the computer and then erasing the slate is bad practice. Photocopying the slate, and then erasing it is a step in the right direction. The best answer is keep your survey data until you are done with it, and then, turn it in to the NSS (or publish, as Mike did an excellent job of doing in Peacock.) If you merely copy your data into the computer and do not keep the original data, there is a very real possibility that some time later (when trying to close a loop) you may realize that you made a "blunder" in your data. Of course, you will then go back to your old data and try to figure out what happened. But where was the blunder? In the transposing from the slate to the computer? Or was it on the original data? Or did you write it onto the slate incorrectly? Who knows? The best answer is to use an actual survey book, with removable pages that you can keep for the duration. Some of you have seen the survey books I use and the underwater cave survey paper that I sell at cost. (Much cheaper than trying to make a little order from Rite in the Rain.)
I cannot tell you how much work I have been saved by people who had "finished with a project" and then turned their data into their local caving organization (in this case the QRSS) who was then able to share it so we could continue to add to the data. Don't be a data hog. You will die some day, and someone else will find a new passage in your cave. Don't make them resurvey the whole cave.

Therion: AAAAGGGGHHHH!! It looks cool, and the one (1) guy who really pushes it loves it, but it absolutely has its limitations. Most of which you will probably never hit. (Roundtripping.)

Ariane: Haven't seen it yet. But 25,000 feet is not a large cave in the mexico (or US) realms. I was just sent a map of a dry cave system in QRoo with (gulP) 100 kilometers!! of passage in an area approximately 7km by 5km. It started with 14 separate cave systems. It's all being done in Walls. Also- if it cant export a stick map, you are wasting your time. You need to be able to get your data out. Walls will export to a shape file, and a KML export is being developed, however you can make the conversion easily in many different programs. You need the stick map export to be able to draw the cave around it. I suppose you could draw within the program? But is that as flexible as using inkscape or AI?

Car comparisons: It's not really the same at all. Those cars all do the same thing. These programs do very different things (except maybe compass/walls) but once you get into the details, and start having the hard questions (how do I tie in my dry surveys and my wet surveys into one map? How do I add survey to a map I have already drawn without redrawing the whole thing? How do I get around long station names?) Only Walls so far has held up to the really difficult projects, and in addition, is still being supported by the developer! It does have a down side, and that is the interface, but as with any computer thing, it seems, the more it does, the more you have to learn about it.

Jason

[FW]

Thanks Jason! Now if it would only clear up enough to do some more surveying.

[jlillest]

Example 2: My 37 mile cave has three entrances.....

Three? What happened to the fourth?

Great stuff Jason, though I'd like to add that over several thousand feet of overland survey GPS coords slowly become a better loss of accuracy (ie more accurate) than a Suunto survey. Also, a GPS point gives a single point and has no effect on the "swing" of a cave passage. Only the actual cave survey can cause the rotational errors that you describe. Even better than GPS points, though, is picking points off of DOQQs if you can find 1m res for your project area. This is very possible for Florida and the rest of the US but may take a while for Mex.

-Jon

[rchrds]

Three? What happened to the fourth?

Great stuff Jason, though I'd like to add that over several thousand feet of overland survey GPS coords slowly become a better loss of accuracy (ie more accurate) than a Suunto survey. Also, a GPS point gives a single point and has no effect on the "swing" of a cave passage. Only the actual cave survey can cause the rotational errors that you describe. Even better than GPS points, though, is picking points off of DOQQs if you can find 1m res for your project area. This is very possible for Florida and the rest of the US but may take a while for Mex.

-Jon

Example. So, three
The DOQQ suggestion is valid, if the entrance is obvious.
The swing described happens when the figure or error is used in plotting the GPS position. Figure the circle of error for a final position at the end- that is magnified by the circle of error inherent in each individual position. Draw the circle around each reported position, then take the worst case location in that circle and use that as a point to find the far waypoint. (ArcGIS can do this automatically, though I haven't figured out how) and check out how large a swing you create. Of course this requires more than one entrance point to pivot about.

Also- Jon, if we do a 3 day (Friday-Sunday in cave camp) survey trip at BSC, you interested? (non diving related, sorry.)

[jlillest]

Also- Jon, if we do a 3 day (Friday-Sunday in cave camp) survey trip at BSC, you interested?

Sure, when did you have in mind? I might even be able to do longer if the objectives justify it.

-Jon