Open Street Maps (OSM) Tile Viewer

[DieterR]

Hi,

I just uploaded an improved version of my OSM Tile Viewer sample app. The major problem of the previous version was, that the GPS position was only correct shown in case of higher zoom levels (>10). The reason was the very simple algorithm I used. Now I spend a few hours in mathematics to find a better solution.

I think, the new version is more than sufficient precise for mobile applications. It shows the GPS position correct within a few pixels for all zoom levels: 0 - the whole earth, up into the range of the GPS precision.
A further major improvement regards to different screen size resolutions. The map will not longer be stretched when other screens than 320x240 are used.

It should be easy for you to add further map tiles side by side to fill larger screens ...

DieterR

[wm.chatman]

Hi DieterR

thank you for your OSM Tile Viewer sample app. The App works great on my HTC HD, with the internal GPS.

Questions please.
Would it be to much trouble to center the GPS Position on the Map?
I would like to use the external Bluetooth Device. The Com Port on the HTC would be Com8. Would I need to change the OSM Tiles Config Settings, in order to use my external Bluetooth Device.
Please Advice.

Edit: I tested your App in the Field on my HTC Unit. Your right, it's off a few Pixels. When Zoom to 14 or 15 GPS Position is a few Pixel's past the real time Position.
As with the external Com8 matter, I have not got this to work yet. Please Advice how this can be done.

Edit: OK. Made a Change in the OSM Tiles Config. Sys.
GPSAuto=false
#COM8 and Baud if Auto=no
COM8
Baud4800
now work's with external Bluetooth Device on HTC.

Another Question please. I would like to use a Label to show Lat / Lon.

Code:
form1.FDrawString("GPS: "& Format(GpsData.lat,"n4") & " : " & Format(GpsData.lon,"n4"),10,2,38,200,56,cBlack)
Label9.Text.FDrawString("GPS: "& Format(GpsData.lat,"n4") & " : " & Format(GpsData.lon,"n4"),10,2,38,200,56,cBlack)
this does not work for me, what would be the correct code for using a label?

Thank you for your Time and Help.

Best regards.

PS> Keep up the great Work on this APP, it's just Great. :-)

William

[DieterR]

Hi William,

Questions please.
Would it be to much trouble to center the GPS Position on the Map?

PS> Keep up the great Work on this APP, it's just Great. :-)

I have already much trouble with this issue. Please, google to "KDR GPS MAP". You can download my "ready to use App" with many features from Heise or my HP. I spend a few hundred hours in it. It works fine for higher zoom levels. But it is a very hard work to improve the precision for lower zoon levels. It requires a very complex computation because of seamless zoom and map moving in combination with the mercator projection of the map tiles.

Another Question please. I would like to use a Label to show Lat / Lon.

The text made by FDrawString might be immediately erased by the function "form1.FErase(....)" when the GPS cursor is refreshed. Either limit the FErase area or create a smal panel and add a label on it.

[wm.chatman]

Hi DieterR

I have downloaded your KDR GPS Map, and tested this on my HTC in the Field.
I noticed that you solved your Zoom and Pixel Problem, and it’s much better now.
Would you maybe be willing to correct the Zoom and Pixel Matter, in your OSM Tile Viewer sample App.?

[DieterR]

Hi William,

I noticed that you solved your Zoom and Pixel Problem, and it’s much better now.

No, these are two very different apps.
In my "KDR GPS Map" the GPS position will not be shown at zoom levels < 8 because it would have a big deviation. The deviation is caused by the linear algorithm used. It does not care the non linear distances within a mercator map. That algorithm works fast and is sufficient precise for zoom levels as used for hiking and biking (12 - 16). In case of proper GPS signals (no buildings, no trees) you can see wheater you are at the left or right side of a street.

I optimized the OSM Tile Viewer to show the GPS position at all zoom levels. I checked it with several significant points in the whole earth view (zoom level 0) and others. (For such verifications I am using a GPS simulator, not the real outdoor site.).

Would you maybe be willing to correct the Zoom and Pixel Matter, in your OSM Tile Viewer sample App.?

Not yet, because the problem is not solved.
Let me try to explain it:
In my map app there are 2 x 9 map tiles in an intermediate layer to assemble the moveable map picture (map background, map foreground, routes and waypoints ...). An area of this intermediate layer is "zoomed" to the screen by using the ImageLib.dll. The GPS cursor is drawn directly at the screen foreground layer because it works very fast. For a correct positioning the map coordinates of the intermediate layer have to be transfered via the "zoom mechanism" to the screen. This computation is relatively complex and slow.

1. An easy solution would be to forget the GPS cursor (and direction arrow) and draw only a GPS track in the intermediate layer. The ImageLib is fast enaugh to refresh the screen every second.
2. For my map app I am thinking about a solution where the new map viewer algorithm is only applied at lower zoom levels.

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Others: In my opinion OSM maps are the best for mobile devices. Why should we not start a new open source project? Later it may be continued with android

Best regards
DieterR