PocketTopo on Windows 10

[caver.adam]

I'm currently trying to get my DistoX2 connected to PocketTopo through Windows 10. I currently use topodroid on a tablet for my survey, but I can't get my calibration below 0.8. I don't have a pocketpc so I'm trying to get it hooked up through a CSR 4.0 dongle. So far I can get the disto to recognize, but I can't get it to connect. Everytime I try it says that I need to "Add a device". But then it says it fails. Sometimes windows even says that the disto is connected in the bluetooth settings window. But PocketTopo freezes for 30 seconds and then gives up.

I'll be working on this more over the next week. I thought I would post here in case someone had a similar experience or had some ideas. I'll plan to post more about what I try and whether I get it working.

My bluetooth in windows 10 shows the disto having outgoing data on COM 7.

[Bob Mehew]

Just a thought, does PocketTopo provide all its functionality in Windows 10?  I got an impression from its instructions that it might not provide the blue tooth function and hence the calibration facility for a normal Windows PC.  I see PocketTopo requires the '.Net compact framework' to be installed when using a Windows PC.  Is that available in W10?  Hope I am not teaching you to suck eggs

I also should admit that in my only try with DistoX2 and PocketTopo, I could not get better than a calibration of 1.5.  Reading around I got a few clues that getting below 1.0 was very good.  Is a value of 0.5 supported by the super surveyors?

[maxf]

I also should admit that in my only try with DistoX2 and PocketTopo, I could not get better than a calibration of 1.5.  Reading around I got a few clues that getting below 1.0 was very good.  Is a value of 0.5 supported by the super surveyors?

Interested to hear about peoples cal results as well, I have currently have 0.8 in topodroid. I have the latest fw/sw installed and tried linear and non linear options.

Trying again in pocket topo is likely to be my next move

[cavermark]

Getting a delta value under 0.5 in pocket topo is possible with care - first take your watch off and anything else that may interfere. Use small points that you can easily find to repeat shots to (eg. I have just used tippex crosses on some local trees). Rather than doing shots from the centre of a cube to each of the faces as the instruction diagrams suggest, imagine doing the sets of 4 shots from face centre to face centre then back again, and same for the corners. This allows you to line up where the laser lines up on the rear end with the marked station points and shoot to the same point. Take extra care with the first 24 readings (the horizontals and verticals). Look at getting the orientation of the device in each rotation correct and 90 degrees from previous (face up, face right, face down, face left). Following same sequence of rotation (clock or anticlockwise every time helps).

[caver.adam]

Maxf is making me feel a lot better about my calibration results. Making me second guess how much work to put into this.

I'm going to listen to cavermark and re-try my calibration being extra careful with my first 24 measurements. I honestly am not sure how well I held the 90 degree rotation on those shots. Especially with the disto face down which was hardest on my clumsy hands.

[Bob Mehew]

Does anyone know if the calibration figure given by PocketTopo is calculated in the same way as TopoDroid?

[maxf]

Maxf is making me feel a lot better about my calibration results. Making me second guess how much work to put into this.

I'm going to listen to cavermark and re-try my calibration being extra careful with my first 24 measurements. I honestly am not sure how well I held the 90 degree rotation on those shots. Especially with the disto face down which was hardest on my clumsy hands.

Make a wooden jig, makes it very simple.

Mine is a 2m long bit of wood with smaller pieces attached at either end. One to rest the end of the disto on , the other for the laser. A small strip of wood     is fitted at one end.

The disto is aligned with the end piece and the side piece and shots taken rotating the disto each time.

This way the heading and inclination is kept constant.

The while jig can then be placed horizontally, vertically or rested against a tree for the diagonal shots.

[caver.adam]

I thought I read somewhere that it was. But its a good question. By the way, which value am I looking at for a good calibration? Error? Or Max Error?

[Bob Mehew]

Without delving into the coding, I am unsure.  But if the quoted error at 0.3473 is a standard deviation, then 3 * 0.3473 which = 1.0419 (being 99+% of the maximum spread of values in the sample population) suggests that the Max Error value of 1.0514 is 3 and a bit times the standard deviation (being the whole sample population).  So in simpler terms that implies the quoted Error and Max Error are linked and one is as good as the other.  Which supports the view that PocketTopo and Topodroid values are the same.

My eye was also caught by the first 4 rows having G in their label (perhaps standing for gravity as in the acceleration sensor) and the next four rows having M in their label (perhaps standing for magnetic sensor) and the ninth row having a L (perhaps standing for length).  Which suggests all three parameters of bearing, inclination and distance are affected by the calibration.  Though as maxf indicated in his post, surely one should be distance checking over a specified much longer distance. 

I guess one might be able to divine from the complete set of measurements used to calibrate the disto how the error value is computed without knowing the coding.  Unfortunately I don't have the time to work on it.  Perhaps asking the authors of the codes might be a faster way of finding out?

[caver.adam]

For topodroid the distance isn't part of the calibration. (I asked Marco).


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[caver.adam]

I can't yet use pocketopo so I haven't asked on that end.


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