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The SexyTopo cave and underground surveying app for Android. Next-gen surveying with a sexy interface.

This app is experimental software made available for free with no guarantee it is fit for anything in particular. I'm not responsible if it loses your data or leads you into some horrific adventure. Caving is a potentially dangerous activity etc. etc. - you know the score :)


How does SexyTopo work?

SexyTopo is an app that runs on Android and talks to a laser measuring device over Bluetooth. SexyTopo builds up a skeleton of the cave using laser measurements and provides sketching tools to fill in the details. It does other things too.

I'm interested in giving SexyTopo a go. What do I do?

You need an Android phone or tablet. The easiest way is to install SexyTopo via the Google Play app store. Just search for "SexyTopo" and click install. It's a very small download.

If you can't access Google Play for some reason (e.g. you're in China) then you should be able to get the APK from here:

What Android device is best to use with SexyTopo?

A large phone or "phablet" (as oppposed to a full-size tablet or small phone) seems to be the best form factor. A Galaxy Note is a good choice. Apart from being about the right size, a proper stylus helps greatly in surveying. Consider buying second hand to get an affordable device for taking underground.

What measuring instruments does SexyTopo work with?

Currently three:

You can also use it in manual mode and input data from old-fashioned analogue instruments if you really have to.

I'm interested in the SexyTopo project; can I help?

Great! Please get in touch. I'm interested in programmers, testers, ideas, etc.! There's also a Facebook group for updates about SexyTopo.

I've had this problem...

If you get a crash (hopefully rare now), please make sure you connect your device to WiFi when you get a chance. A very basic error report will get uploaded if SexyTopo gets a chance (please also select "Send Error Report" for best results). A bug report email with more details is also super-useful.

What import / export options does SexyTopo have?

Sexytopo understands the following formats. If you are interested in helping SexyTopo understand other formats, please contact me.


  • TherionSurvex (data)
  • PocketTopo .txt export format
  • SVG
  • Compass (not written by me, haven't tested how well it works)


  • Therion (Therion files produced by SexyTopo and other simple Therion files)
  • Survex (Survex files produced by SexyTopo and other simple Survex files)
  • PocketTopo .txt export format


The SexyTopo cave surveying app for Android




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