Monday, July 04, 2005

Pocket Topo!

I decided to build my own dedicated Pocket PC GPS. There are a couple of good choices regarding software and hardware for PDA's out there. But National Geographic Pocket Topo! was my first choice among quality image handling and precision.

If you get Backroad Explorer, a package that includes Pocket Topo, you can select an area from say a State Series map and transfer to a PDA as a .tpo file.

After getting all worked up about a silly and devious bug (lack of support for NMEA GPPLL sentences) finally got a hang on the combination of a Holux GPS CF Card (GM270 Ultra), a Toshiba e755 and Pocket Topo! from National Geographic.

NG published digital maps based on scans of USGS Level 5 topographical data. Same as the 7.5 minutes, printed versions. The scale is 1:24,000.

It did trick me for a while, but watching "Finding Neverland" it happened.
The bug is that if you select NMEA GPGLL (Geographic Position, Latitude, Longitude) you will have the cursor repainting the same position in the screen forever in a infinite loop while trying to obtain data from the receiver without actually printing anything.

It will work for NMEA GPGGA sentences (for Global Positioning System Fix Data which includes Time, Position, Elevation). And it was a relief to see the little yellow breadcrumb left behind while moving in a 7.5 degree map of Santa Cruz, CA.

Transfering Maps to SD Card

Pocket Topo didn't recognize the SD Card while looking for storage options in the PDA. I had to use File Explorer to create a new folder and transfer the .tpo files to it.

But I have to say that Topo, as a package is just the ticket: get a State Series CD collection ($70), add Pocket Topo! (notice the NMEA GPGLL bug), a PDA like the Toshiba e750 series and a good, low-consumption Sirf-based GPS CF card.

The battery life is the main factor about how you would go about using such device. eBay has several battery expanders for the e750 for about 50U$S including around $7 S&H.

The nominal value of its charge is 3,000mA (miliamps).

Pocket Topo! on Palm

I haven't tested myself, but everything said about the PocketPC version of Pocket Topo! applies to it. Check the NG site for a patch for HotSync at


Anton said...

So you were able to use your external memory card to store tpo files?

I've been trying to accomplish this on my palm device without success.

What sort of directory structure did you create on your card?


gpsguy said...

In the Pocket PC you only need to point to the directory where the .tpo files are located. Either in the local storage or a SD card. Nothing special there.

gpsguy said...

I never quite answered this one... PPC uses a FAT directory structure. Not sure what the Palm OS does.