Increase precision of GPS coordinates

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Increase precision of GPS coordinates

Postby MichaelStranks » 2019-03-14 0:08

I am on the trial version of Map Plus, and it seems to be working great for me.

I noticed, however, that the most precision that the GPS coordinates will do is xxx.xxxxxx 6 decimal places. This is roughly 11cm accuracy. I would like to use the app with a GPS system that is capable of RTK accuracy, getting closer to 1cm. Is there a way to increase the precision to 7 or 8 decimal places? For both position and points (and imported points for that matter)
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Re: Increase precision of GPS coordinates

Postby Zax » 2019-03-14 2:37

MichaelStranks wrote:I am on the trial version of Map Plus, and it seems to be working great for me.

I noticed, however, that the most precision that the GPS coordinates will do is xxx.xxxxxx 6 decimal places. This is roughly 11cm accuracy. I would like to use the app with a GPS system that is capable of RTK accuracy, getting closer to 1cm. Is there a way to increase the precision to 7 or 8 decimal places? For both position and points (and imported points for that matter)


Please notice that the 6-decimal-digital coordinate is just a "display" format, internally, the app save and process coordinates as a double float value, which actually get 15 to 16 decimal-digital for the accuracy.

The display value formatting has nothing to do with importing and exporting, it is never saved, it is dynamically generated when screen needs to display a coordinate.

By the way, if you try to edit a coordinate by value from the detail information, the input field would be initialized with a display formatted value (6 decimal digital), you can input a more accurate value with any decimal digitals there, but if you do nothing and tap "Save", the truncated display coordinate (6-digital) would be saved and replace the existing accurate one. And this is the only way that a display coordinate affects the stored coordinate.

More, currently, the CSV and KML exporting might also use the 6-decimal digital for those text-base formats, if you requires higher accuracy for exporting, please use binary format such as SHP, TAB.
And please notice the importing of these text formats do not have such limits, all coordinates would be imported accurately.
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Re: Increase precision of GPS coordinates

Postby MichaelStranks » 2019-03-14 14:28

Zax,
Wow, thank you for your quick reply.

That makes sense to me.

Is there a way to zoom the map in further in the screen? I see that using different base maps will limit the extent that you can zoom in, but I was wondering if I can go still further, again, an issue with getting down into cm accuracy.

Thanks for your help!
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Re: Increase precision of GPS coordinates

Postby Zax » 2019-03-14 14:44

MichaelStranks wrote:Zax,
Is there a way to zoom the map in further in the screen?


The max zoom limitation changes only for different system map layers, which indicates the Apple's Road Map, Satellite Map, Hybrid Map, etc.
While chosen the System Map as "Apple Road Map" or "None", it provides the max zoom level to about lv. 20.

Sorry but this limitation is applied by the underneath map engine we are using, the iOS's MapKit, we could do nothing for it if we still use that map engine for basic map content presentation.
We are expecting that Apple may drop this limit in a future with their new iOS updates, at that time, you can update the iOS and get more zoom levels to zoom in.
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Re: Increase precision of GPS coordinates

Postby MichaelStranks » 2019-03-14 15:58

Thanks understandable.

So by importing my own base map, I could maybe zoom in further? I see that I can do that. What format does that map need to be in to use it?
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Re: Increase precision of GPS coordinates

Postby Zax » 2019-03-15 7:29

MichaelStranks wrote:So by importing my own base map, I could maybe zoom in further? I see that I can do that. What format does that map need to be in to use it?


Switch between different system maps is the only way to change the max zoom level. Choosing "Apple Road" or "None" as the system map provides the largest max-zoom-level of MapKit, about level 19 to 20. (level 0 is world map of 256x256 pixel, each level enlarge the width and height by 2 times)

Adding or switching custom map layers or vector data layers has no effect on max zoom level of the map canvas.

More about map layers:

There are two kinds of base maps:

1. System Maps.
Which indicates Apple's embedded map(road, satellite, hybrid...), they are embedded with iOS, same for all apps that uses the iOS's MapKit as the basic map engine.
You can choose and view them, but can't not adjust their too much like other custom maps, for example, limit their boundary, transparency, overlap order, download region for offline usage...
Different choices of system maps affect the Max Zoom Level of the whole map canvas, this restriction is managed and performed fully by the iOS MapKit, our app could do nothing on that, we don't know when and how it is changed, neither could the app to get the current max zoom level. (If iOS drop or ease this limit some day, you can zoom in more without any update or setting to make in the app)

2. Custom Maps.
You can now add Google, Bing, USGS, Open Street, ..., and any other popular online maps to the app, or maps published with standard map services such as WMS or WMTS, just by providing a configuration (the key of that is a URL pattern), then you can view them as a editable custom layer, together with any other map content, including system maps and your vector data. It is a free function which also provides capability to set styles, crop boundary, transparency, lay order, offline mode, cache management, etc. More, you can make a download map from any of those custom maps for a spec region and zoom levels, which makes a download tool for all popular map services (although you have to take full responsibility for any copyright risks for those downloading and using behaviors).

Check this for more about using custom maps:
http://duweis.com/support/viewdoc.html? ... _onlinemap

Adding or switching custom maps have no effect on the map canvas's MAX zoom level, which only depends on the current system map you choose. If you choose None as the current system map, the max zoom level is just the same as "Apple Road Map". (Actually, the MapKit does not support "None" for system map, so choose "None" is tricked by just overlapping a single color overlay on top of Apple Road Map so that user couldn't see it.)
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