[closed] Wrong angles reading

[1echeck]

Angles reading is not right. Neither in NATO mils or Soviet mils, there is always 26-27 (24-25) mils difference. Can you please explain how to fix this? I would buy the full version then.

[Psyberia-Support]

Hi,
Can you give more details on the problem you have?

[1echeck]

Of course, thank you for quick response.
E.g. two points are set:
1st E48000 N70000
2nd E49000 N70000
Bearings between these two points must be 90°/1500 mils (Soviet)/16-00 mils (NATO) etc.
But the readings says 91,6°/1526 mils (Soviet)/16-28 mils. By readings I mean putting those two points in the map as waypoints and then set one as a "target" and second as "jump to'.
It seems like the map grid is little rotated or something?

Thank you again

[Psyberia-Support]

The bearing of the UTM/MGRS grids are not aligned to meridians and parallels, so you don't have 90° between easting points.
In this screenshot you can see the long/lat grid in black, the North is up and in blue you can see that the MGRS grid is not aligned on them...

screenshot.jpg

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[1echeck]

Ok, now it's clear, thank you very much! Here comes the important part: is there any way to align them? I know a lot of guys who would really appreciate it (and buy full version as well as me)

[Psyberia-Support]

The application already support most of map projections so you can reproject your map to match the MGRS grid, but:
- The bearings will still be the same (they don't depends on the map projection), so you'll never get 90° between easting points. That's the way the MGRS grid is build, it's not related to the app.
- The MGRS grid changes direction every 6° of longitude, so your map will only be aligned in a particular area (you can see on the image below a junction between two grid squares that the grid lines are not stable).

slide_44.jpg

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Currently, the application uses the map projection of the bottom most map, and reproject all maps added as layers (if needed). So to align your map, you need to first display (or manually create) a map that use a projection matching the MGRS grid at the location you want, then you can add any maps on top and the application will reproject them in this projection.

I've created a fake map using the MGRS projection (EPSG:32631) on the previous example area as a test. On the left, the map uses the projection of the OSM map, on the right, it's reprojected to be aligned:

reproj.jpg

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I agree it's not technically easy, but I don't really see a practical usage of this. I also attach the map definition file (.aqx).
Anyway I'll see if I can add a setting to easily force the projection...
Let me know if I haven't correctly understood your request.
Best regards

[1echeck]

This is exactly what I thought. Your explanation is perfect. I am well aware of MGRS system and the simplicity of it, which is for military purpose very useful. However, in situations like this (using your application) it becomes kinda difficult. We are trying to use your app for military training purposes. Artillery reconnaissance units need to use all kinds of grids (as shown in the app) and bearings. We calculate geodetic formulas using polar grids and many more kinds of operations. We need to be as accurate as possible. So if there's any way how to make it work (I understand its difficulties), it would be a great help for us. I can imagine manually aligning (setting some value to rotate?) each map area used in concrete area. Our line of work is setting some observation post and measuring angles, acquiring possible targets coordinates according to measured angles and distances and adjusting fires on them.

Thanks again

[Psyberia-Support]

With the last app version you also have another very simple solution.
In the app settings, be sure to check the option "Manual map rotation" so you can manually rotate the map and align is to the MGRS grid. When moving over another area, just rotate the map a bit more...
Here is the result:

device.jpg

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[1echeck]

I can rotate the map but the reading is still the same On the screenshot you can see "First point left" set on 48000 70000 and bearing from the "Second point right" set on 49000 70000 is always 16-28 instead of 16-00 as shown on the picture a way too below that first point. Doesn't matter how do I turn the map..

[Psyberia-Support]

For me, the angle between
1st E48000 N70000
2nd E49000 N70000
is 91,6°.

I think this is where the problem comes from, it's just a misunderstanding... All angles in the app are relative to the True North.
So the app does give the correct value.

[1echeck]

It has been agreed so military (or anybody) can easily count with these values. For instance here https://en.m.wikipedia.org/wiki/Milliradian
That's why MGRS is used by army instead of LatLong

[1echeck]

Here you can see the calculation of inverse geodetic problem in WGS-84 (MGRS) using mils(NATO). Full circle has 6400 so it has to be 16-00

[1echeck]

Is there any chance you could fix this little error? We always have to subtract 28 mils to be accurate, which is kinda annoying..

I say again, we would buy the full version then.

[Psyberia-Support]

I'll see what I can do but I cannot give you any guarantee.
This is not just something to fix, it's a new feature to add. You need computation based on the grid north, whereas it's currently based on the map north. It's not the same thing and it's not wrong the way it currently is.
Most users need the computation the way it is now. The grid north is mainly used for military, whereas this application is mainly for recreational users. If I just change this, lots of users won't be happy, not I need to also keep the current method.
I'll let you know as soon as possible, should be within one month before the next version.

[Yemble]

Surely the military (of whichever state) should be providing additional funding for such bespoke development?