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  • Technical Details

    Here are some more technical details for those who wish to use programs other than Google Earth to make Garmin Custom maps or want to make some more advanced maps.
    • It is ok to have more than one jpeg inside the kmz file.
    • doc.kml, inside the kmz file, is the only kml file that will be processed.
    • Jpegs are the only type of image supported.
    • kmz files are read from \Garmin\CustomMaps directory on both the unit's internal memory and on the sd card.
    • Images over 1 mega pixel (1024x1024 pixels, 512x2048 pixels, etc.) will be rendered at a reduced resolution on the unit. If this is causing a problem for your map, you can split the image and use multiple jpegs inside of one kmz file. Here's an example of a map has an images that has been split into 4 jpegs.
    • Each jpeg should be less than 3MB.
    • The max number of Custom Map jpegs you can load is 100. (500 jpegs on Montana, Oregon 6x0, and GPSMAP 64)
    • The time it take to draw the map is directly proportional to the file size of the jpegs being drawn.
    • These are the xml tags that are processed by the unit:
      Code:
      <kml xmlns=....>
      <GroundOverlay>
      	<Icon>
      		<href>files/CentralParkRunningMap.jpg</href>
      		<DrawOrder>0</DrawOrder>
      	</Icon>
      	<LatLonBox>
      		<north>40.80531332719471</north>
      		<south>40.7601597052842</south>
      		<east>-73.95274155944784</east>
      		<west>-73.97364085195952</west>
      		<rotation>-28.77996170942711</rotation>
      	</LatLonBox>
      </GroundOverlay>
      </kml>
    Last edited by TRAILTECH; 05-16-2014, 08:37 AM. Reason: added GPSMAP 64

  • #2
    Above you've indicated that the max number of jpegs is 100 -- is that per KMZ or a total limit on the entire unit?
    GPSFix
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    • #3
      That is total across all kmz files on the unit.

      Comment


      • #4
        So if I take this to its logical extreme:

        - 100 files max
        - 1024x1024 max file resolution to avoid reduction in resolution on unit
        - max land area covered by each tile is about a square mile (this guarantees that you don't get pixelation at 200'-300' zoom level and out based on my math)

        The max you can map using this feature is about 10 sq/miles. I could go to 20 sq/miles if I was willing to live with pixelation below the 500' zoom level
        GPSFix
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        • #5
          Can you elaborate more the DrawOrder?

          If >50 it draws over Garmin maps
          If <50 it draws under Garmin maps (can you see any of the custom map or is it entirely blocked).

          Is there a level at which waypoints, tracklogs etc will be covered by the custom map.

          And I'm assuming if I have different custom maps at different levels the unit will layer the higher numbered map over the other?
          GPSFix
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          • #6
            If you cover one square mile with each 1024x1024 image, then you should be able to cover 100 square miles with 100 jpegs. I think you will find the resolution you want to use will vary based on what type of map you are making. For many maps you will need to use one mega pixel to cover a square mile (about 1.5 meters per pixel). Some maps aren’t as detailed, and nothing is lost by using fewer pixels per meter. For example, the Samuel R. McKelvie National Forest map uses about 11 meters per pixel. That’s all the detail that the original map provides. However, this map can still be very useful. The text is clear, and the trails and windmills are identifiable.

            A DrawOrder >= 50 will draw on top of other maps. A Custom Map with a DrawOrder <50 will draw on top of the land, water, and areas on other maps, but roads, topo lines, and depth contours will draw on top of the Custom Map. Waypoints, tracks, routes, geocaches, POIs, etc will always draw on top of Custom Maps. Custom Maps are drawn with higher DrawOrder maps on top of CustomMaps with a lower draw order.

            The Central Park Trail Map is an example of a map with Draw Order <50. The University of Nebraska Football Parking map is an example of a map with DrawOrder >= 50. If you load the Golden Gate National Recreation Area map and the Alcatraz Island map at the same time you will see the Alcatraz map (which has a higher draw order) drawn on top of the Golden Gate map.

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            • #7
              Thanks that helps. And of course you are right about it being 100 sq/miles vs. 10
              GPSFix
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              • #8
                One more question. Are superoverlays supported?
                GPSFix - Garmin Outdoor GPS Blog
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                • #9
                  Originally posted by GPSFIX.COM View Post
                  One more question. Are superoverlays supported?
                  They are not supported.

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                  • #10
                    I've seen posts from a number of people who can see the Custom Map button in Map Setup but cannot see the map on the map page.

                    The speculation is that very large images may not show up on the map at all. Can you confirm if this is true and if so is there some upper limit to the size of a image that the unit will display?
                    GPSFix - Garmin Outdoor GPS Blog
                    Garmin Oregon Wiki
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                    • #11
                      No single jpeg should be larger than 3MB. The time it take to render a custom map is directly proportional to the file size of the jpegs. Saving jpegs with a quality of 80 can greatly reduce their file size without losing much quality.

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                      • #12
                        The 1024x1024 restriction is mighty limiting. We're going to need some sort of map tiling s/w to get past this one.

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                        • #13
                          I've been playing with this a lot for the past couple days. What a great feature - a big THANK YOU to all the members of the team who have worked on this!

                          I have made several maps with New Jersey 2007 digital orthophotography at 1 foot per pixel native resolution and they look fantastic. I have a LOT of this imagery in Globalmapper already, so making the Garmin custom maps was trivial - just a few mouse clicks to export as .kmz. Here's an example at different zoom settings on my Oregon 400t



                          At this resolution with 1024x1024 tiles, the math is pretty easy. 5 tiles will be about a mile wide. So 10 tiles x 10 tiles gives you an image 2 miles x 2 miles (4 square miles) and a total of 100 individual tiles. The map in the example above had about 80 tiles, which is close to the limit. Sure, I wish we could cover a large area, but this is still really cool.

                          I use OziExplorer CE extensively and have been making maps from the NJ 2007 imagery sampled at 4 feet per pixel which look pretty good also. At this resolution you could make a Garmin custom map covering an 8 mile x 8 mile (64 sq mile) area. I have also found that the USGS 24k topo's from terraserver can be sampled at 10 feet per pixel and not lose much detail. So we can make custom maps from these which cover an area about 20 miles x 20 miles (400 square miles).

                          -Boyd

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                          • #14
                            Will it be possible to set different images for different zoom levels (scales)?

                            Raster maps have limited zoom in/out range when they remain readable. It would be nice to be able to use different scale raster maps for different zoom levels.

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                            • #15
                              In the maximum of 100 jpgs a technical limitations regarding to memory or speed of display ?

                              Will you increase this limitations in the future ?
                              Thks

                              PS: Anyway, this custom maps feature is a BIG improvement !!! This is just awesome

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