Map Prefetch & Saving


Lynn Deffenbaugh
 

Bradley Haney wrote:
Lynn, your software is awesome. Been using in my. Old hp travel companion and kenwood d700. Works wonders. I have a bluetooth. Serial adapter plugged into the radio. So its all wireless.
Thanks for the kind words. I've seen your snowmobile running around and tried to send a message to you the other morning, but apparently there's no bi-directional IGates in your area because I didn't receive any acks. I was wondering if you were really on a snowmobile or in a car that was wishing it was a snowmobile!

One question. How do I save maps so I do not have to have a data connection going all the time. I would only really need about 3 counties of maps
There's a menu option under View / Maps / Prefetch that will handle the prefetching of the maps. Then you need to edit the XML file to make sure the map tile purger doesn't do away with them. Here's the procedure:

Only do the following when you have an Internet connection and time to wait for the prefetcher to pull in the map tiles! We're talking thousands of them!

1) Zoom and pan the map so that an area of interest is all that is visible. On Win32 you can even size the window to help focus on the interested area.

2) Select View / Maps / Prefetch. The client will tell you how many tiles cover the area including several zoom levels closer. Don't panic, this will be a large number!

3) Once you click Yes, the client will queue all of the missing map tiles. This can take a while (even just to queue them) so be patient. Once all have been queued, the actual count will be displayed. This may be less than the original count because some of the tiles have probably already been cached.

4) The yellow circle will begin expanding as the tiles are fetched, but you don't need to wait for it. Double-clicking an empty spot on the map will provide you some visibility into the queue length and the states of the threads doing the retrieval.

5) You can now repeat steps 1 through 4 at various zoom levels to make sure you have all of the tiles you want. If you miss some, the client will simply stretch the next higher zoom level to cover the hole if/when you get into one.

OK, about 5 minutes after the yellow circle has expanded and disappeared, double-clicking an empty spot on the map will tell you the current state of your cache. For example, my Windows Mobile has 8,386 tiles over 38.77MB while my desktop has 55,349 tiles over 323.41MB (yes, I zoom all over the world from my desktop). So, how do I make sure they don't get purged. You edit a hidden parameter in the XML file!

1) Close the client. If you don't do this, any changes you make to the XML file will be lost when you DO close the client as it is completely rewritted by the client on close.

2) Locate and edit APRSISCE.xml (or APRSIS32.xml). On Windows Mobile, it will be in your My Documents folder and probably synched to you desktop. Make sure you wait for the sync to finish after closing the client. On Win32, it will be in the default directory where you run the client.

3) Edit this file with a plain text editor. You're looking for a tag called <OSM.RetainDays> which is probably set to something like 7. Change that value to 0 and it will disable the Tile purger and keep everything you've ever fetched.

4) Save the file and wait for it to re-sync back over to your Windows Mobile device before restarting the client.

You can still pre-fetch additional tiles whenever you have a connection. However, when you're going to be connectionless, I would recommend unchecking the Enables / OSM Fetch Enabled. This will prevent the client from even attempting a connection to the OSM server for any missing tiles in the event it needs one while you know you'll be out of coverage.

Oh, and if you think about it, please send me the string of numbers from the OSM Map Tiles popup that starts with Sec: and has 5 numbers after it. These are internal timing numbers that gauge the various phases of the Tile fetcher. You have to do this after the prefetch queue has completed and BEFORE you close the client. Knowing these numbers might help me do some performance tuning on the tile fetcher in a future version.

And finally, if any of you actually do this procedure, let me know how it works out when you go Internet-less. My son, KJ4DXK, is planning to run in this mode with his home-brew tracker, but he still needs to do some code on his end before he'll have it in operation. I'm anxious to know if it actually works!

Lynn (D) - KJ4ERJ - Author of ARPSISCE for Windows Mobile and Win32


Bradley. Kc9gqr

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