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Author Topic: Missing Data Along Borders When Stitching Maps  (Read 2550 times)

grclark888

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Missing Data Along Borders When Stitching Maps
« on: June 10, 2010, 12:08:10 PM »

I'm using a 60Cx.

Maps downloaded from GPS depot for Nevada and Arizona show all appropriate data.

Sending data to my Garmin with MapSource, along the borders of states, I find that one states data will over write the other states data for the same sector and do so in such a manner that I can not control it.  Map segments of one state may have blank areas over the border for the adjacent state's data.

Here is a specific example using the Arizona topo and the Nevada topo:

Nevada topo segments Topo K-7 and L-7 the Gold Butte areas west of the Arizona border, south of I-15, north of a branch of Lake Mead.

Arizona topo segment B-1 that overlaps Nevada L-7

The Nevada L-7 has all the topo data, the Arizona B-1 is blank for the Nevada section of the map segment. The Arizona segment always trumps the Nevada segment when these are transferred to the device so that Nevada data is replaced with the Arizona non data.

I see no way in MapSource to arrange segments or prioritize segments such that the Nevada data trumps the Arizona non data for that area.

There appears to be no way to nudge MapSource to use the Nevada segment and always applies the Arizona blank segment.  Any ideas for a fix for this since there may be other blank areas in a stitched download with no data and I'd like to find that out before hitting the back roads.

grclark888

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Re: Missing Data Along Borders When Stitching Maps
« Reply #1 on: June 10, 2010, 12:52:52 PM »

So there is no 'standard' to to trim at the border and not interfere with adjacent states?  It seems that the CA topo, by the nature of CA running at a diagonal along its eastern border, doesn't interfere with the NV topo even though there is overlap all along that border since the segments are rectangles.  So when we download and make a chip with multiple states we need to check all of the border areas?  I don't know anything about making maps, I was just surprised that blank data sets can supersede data sets of another state, and that some maps play nice with border states, and some don't.

Boyd

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Re: Missing Data Along Borders When Stitching Maps
« Reply #2 on: June 10, 2010, 01:09:11 PM »
Yep, that's the way it works. It is completely up to the mapmaker to decide how to deal with this issue. If you buy one of Garmin's products, like US Topo, it will be seamless. If you mix and match user-contributed maps, the results will not be consistent.

Maps have a draw order (again determined by the author) which determines which one will be drawn on top of the other. You cannot do anything to change this on your GPS or in mapsource, it is hard-coded into the map file.


Boyd

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Re: Missing Data Along Borders When Stitching Maps
« Reply #3 on: June 10, 2010, 02:41:47 PM »
The nice thing about standards is that there are so many different ones to choose from.  ;D

Seldom

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Re: Missing Data Along Borders When Stitching Maps
« Reply #4 on: June 10, 2010, 03:37:55 PM »
Border overlaps wouldn't be a problem if the maps were transparent would it?  Might be a few misaligned countours, but as long as you turned off your non-transparent products it should work.

grclark888

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Re: Missing Data Along Borders When Stitching Maps
« Reply #5 on: June 11, 2010, 05:23:07 PM »
I just sorted my maps onto separate chips and grouped the ones that played nicely with each other.  CA-NV-UT, ID-MT-WY, AZ-NM-CO,  WA-N West-N Central & AK.  The AZ and NV maps are on separate chips now so no worries.  Kinda like having in-laws that don't get along.  Thanks for all your input.