.ov2 file layout

peteheff · Occasional Visitor Joined: Oct 23, 2004 Posts: 4

I have had a quick search and found nothing (wrong criteria maybe)...

Could someone here point me to where I can get the description of the seven bytes preceding the text in the .ovl file please?

Just out of interest I had a look at these files and set about trying to translate Degrees/Minutes/Seconds to those bytes but fail miserably so far Sad

Also, could someone tell me why we use an negative number rather than just a full 360 degrees; I'm sure there has got to be a good reson for it..but I'm blind to it. If someone has an answer I'd appreciate it

lbendlin · Posted: Sun Oct 24, 2004 12:03 am Post subject:

The negative number is because of Greenwich. Everything east and north of it is positve, everything south and west is negative. I am talking about Lat/Lon, of course.
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peteheff · Occasional Visitor Joined: Oct 23, 2004 Posts: 4

Thanks lbendlin.

So why use negative numbers then?

If -1 would map to 359, -2 to 358 etc. it seems to me that degrees/minute/seconds could be held in 2 bytes of data rather than messing with negative values.

What am I missing? (first time I've actually considered this, so, be easy on me)

pete

peteheff · Occasional Visitor Joined: Oct 23, 2004 Posts: 4

Apologies for the double post, but I can't see a way of editing the previous one.

If Greenwich = 0 degrees then Greenwich also 360 degrees, so, left of Greenwhich = 359 60' 59" or less?

pete

lbendlin · Posted: Sun Oct 24, 2004 12:23 am Post subject:

it's still the same two bytes. It's not going to -359 degrees, the range is from -180 to +180 and from -90 to +90 - just like a normal integer. (ok, similiar, but you get the point)
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lbendlin · Posted: Sun Oct 24, 2004 12:50 am Post subject:

Here's the structure

Lead-In 02 1A 00 00
Divider 00
Longitude (three byte, LSB) for example 7D 59 6C
Divider FF
Latitude (three byte, LSB) for example D6 2A 2E
Divider 00
Text (zero delimited)

and then all over again.

But why bother? There are programs around that convert OV2 to TXT and back.
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peteheff · Occasional Visitor Joined: Oct 23, 2004 Posts: 4

Is there a .doc file that explains this in some detail lbendlin?

I'm just curious about this now, and don't want to waste your time.

..and would that .doc file go as far as explaining the layout of the .ov2 file?

thanks,
pete

lbendlin · Posted: Sun Oct 24, 2004 3:30 am Post subject:

nope...

search for makeov2.exe and dumpov2.exe
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barryd · Posted: Sun Oct 24, 2004 4:50 pm Post subject: OV2 file format

The OV2 file format is documented in the TomTom Navigator SDK manual here (it's a 100k PDF file):
http://www.tomtom.com/support/ce/downloads/ttnavsdk_manual.pdf
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