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Aerial images

Started by Lucky Dog, June 26, 2022, 07:53:47 AM

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Lucky Dog

Is there a source out in the internet world for aerial images that can be incorporated into map making software?

I'm using Mapwel, and my end goal is to make IMG files that can be loaded into my Garmin devices.

I've been using Garmins Birdseye, but that product has been mostly discontinued.


Many states have their own free imagery, the quantity and quality may vary. But I would start there with a few Google searches such as this (substitute your state name)

michigan gis data
michigan orthophotography
michigan orthoimagery

The USGS National Map has NAIP (National Argriculture Imagery Program) imagery for the whole US at 1-meter resolution, they are in the process of upgrading the resolution. They shoot this every year during the growing season on a rotating schedule to cover all US counties. However, depending on your needs, this imagery may not be as useful since the tree canopy hides a lot. The individual states generally have imagery shot durig the winter when trees are bare.

Anyway, you can go to the National Map downloader and check the imagery/NAIP box to find what is available in your area.

Now for the hard part... Mapwel is not the tool to use for aerial imagery. It can convert raster imagery into Garmin's format but the result will be really poor by today's standards. I spent quite a long time using Mapwel, MOAGU and ultimately writiing my own software for this. I used to offer a map of the Mid-Atlantic region with aerials that I converted to Garmin's format. Recently I discontinued that map because the quality just isn't there. The best I was able to acheive was ~50 feet/pixel and Garmin automotive devices really stuggled to handle that. Garmin handhelds just couldn't handle that at all and would either crash or operate in slow motion.

If you want aerial imagery, you need to use a raster format. The simplest choice is Garmin Custom Maps (.kmz files) but these are limited to very small coverage areas - 100 tiles at 1024x1024 pixels on most devices. There are only a few handhelds with a 500 tile capacity. Even then, coverage is pretty awful.

Using 1-meter imagery, 100 tiles will cover an area 10km x 10km (~6mi x 6mi). If you use imagery with 1-foot resolution, you can only cover about 2mi x 2mi. The best solution is to use software that can covert your imagery to Garmin's birdseye format - .jnx files. I don't think there is free software for this, but could be wrong. I know that OKMap can do it, but it is not free.

Mapc2mapc is another paid app that can do this although I have not used it myself

Once you put the imagery into .jnx files, you can trick the GPS into believing it is real Birdseye. However, you need to have an active Birdseye subscription for this to work, and the whole thing is complicated and unintuitive. I have done this myself (with OKMap) and made a map of most of my state with my own imagery. I then made a transparent .img file overlay in Garmin's standard format to display roads, cities, etc. on top of the aerial imagery. I still use this on my Garmin DriveTrack automotive GPS, which is compatible with Birdseye and custom maps.

Now, whatever you download will likely be in geoTIFF files (or possibly JPEG 2000), so you will need software that can open that and covert to one of Garmin's formats.

This is all way to complicated and now I'm out. Not making any more Garmin maps - they could make this easy for everyone but they won't, because they don't want people making maps that compete with their paid products.

Anyway, there are some ideas for you. Unless you just want to make a map of a very small area, it is going to be a pretty frustrating exercise I'm afraid.


Yes, MAPC2MAPC (I'm the author) will make JNX files from most image formats. It will use GDAL (free) for the more complex ones like ECW. It is free to try.


Awhile back I was messing around and the end result I snipped out, the ingredients:

-Map in basecamp, in this case I had made a custom map of one grid of lat/long
-I used  In this case I believe I used an ESRI image and exported to kmz format
-Import in basecmap and played around with transparency and detail settings
-I don't remember which I did first but I sent to gps (orux, old etrex and newer etrex)

The end result was "passable" for my purposes, but I haven't put any more effort in this.  This image is of the Eagle Cap Wilderness in NE Oregon.  I've been doing some side stuff in relief shading and have used use sas, there are also a couple of plug ins for qgis that allow you to add layers from various aerial imagery sources and then save/export to other formats


That is pretty cool. Where does the 3d terrain come from in your screenshot. Is that Basecamp? Google Earth?? Or are you making your own Garmin-format DEM?

I made my own 3d map of North America using the Mapbox API with ASTER DEM, USGS NLCD and ESA Worldcover data. Not familiar with Eagle Cap, but assume it is somewhere around here?

(use the right mouse button to tilt/rotate the map, or two-finger gestures on a touchscreen)

But this is not something that can be done with Garmin's software or devices.  :)


The screenshot or "snipping" was in basecamp, then I cropped a little more with an image editing software.  In 2018 or so the MKGMAP folks figured out how to "merge" the SRTM data (.hgt files in this case) in the compiler as an option, in the simplest term.  For shading and basic 3D the 3" are fine for basecamp and gps and they are 2.75mb for each tile vs 25mb for the 1".  My US-WestTopo uses about 440 2.75mb tiles, the 1" would make the map way to big and strain my hard drive capacity from all the other maps!


Cool. 8) Can your Garmin handheld GPS also display the map like that (photorealistic 3d view)?

The map in my link above is about 100gb (4 million tiles) and my high resolution LIDAR 3d map of the Mid Atlantic states is 260gb (10 milliion tiles). Am currently working to expand coverage which should end up around 600gb (maybe more?) later this summer.  :)


Neither of my handheld garmins will display a photorealistic 3d, though they will show the 2d version, whatever is in the map and the kmz image that was overlaid show up.  Orux maps will show 3d, not natively though.  The gmapsupp, even if shading is in the img, will not show up.  One has to copy to the DEM folder in orux the .hgt file(s) and point orux to where that folder  is at.  One then may have to adjust the altitude scale to avoid overly pointy or flat terrain.  The zoom and tilt work well, but text and trail, roads gets distorted somewhat, it looks fairly close to the basecamp version though.  It's fun to make and can be useful, but one has to accept some limitations.

When not currently used I 7zip my contour and dem files and it's about 40gb or = 4 Tb unzipped.  Any map the has images or terrain has a storage tax.  This would be difficult if not impossible for mortals 15-20 years ago.  With this app you have created, are there any sd cards of that size to hold 600gb? 


So how much area is covered with your 40gb dataset? There must be something very inefficient about the file format if you are getting 100:1 data compression with zip! My maps consist of .png map tiles (was not satisfied with the compression artifacts when I tried .jpg). So when I zip them, the size is basically the same. However the source data DEM files are uncompressed geoTIFF and they are about 10x the size of my final product.

Mine is a web app so all the data stored on my server, no SD cards are needed. That is my medium now, it makes my maps easily accessible to anyone on both computers and phones with nothing to download or install. Of course, Garmin handhelds certainly have their uses but I'll leave it to you and others to make that kind of map. I spent many years making Garmin maps, but just got frustrated with all the limitations.


My bad on my math.  It should be 400gb not 4tb.  Each region I've made has a folder and within are the hgt files for dem and mp for contours.  Say it's 20 gb uncompressed, zipping in 7zip format, set to ultra it will end up about 12% of the folder.  I delete a folder when not needed and decompress the archive when needed.

To the OP, I don't have numbers to back it up, but leading up to and beginning to make maps for garmin devices I concluded that there aren't that many people making them, though the small community is dedicated.  It is dispersed over place and time with free software, depreciated or no longer available software mixed in with paid.  You have asked about aerial images and some suggestions have been made where to locate them.  When I first began making maps there wasn't or really isn't a one stop shop and I had to figure a lot out by testing and trial and error, for my purposes, and I'm glad I did.  Good luck.


Getting back to aerial imagery... in your earlier post you said

Quote from: sockmonkey on June 27, 2022, 03:30:12 PMFor shading and basic 3D the 3" are fine for basecamp and gps and they are 2.75mb for each tile vs 25mb for the 1".

At first I didn't understand this, but then realized you were using the quote character to denote arc-seconds, in other words 1" = one arc second. Is that correct? And I also assume you are only talking about the DEM? Of course, one arc-second would be really low resolution for aerial imagery.

The comparison below might be useful for the OP. IMO, you want at least 4 feet/pixel resolution for hiking but 1 foot would be even better. The last example is a 30m or 1 arc-second view of the same area.

With a 100-tile limit for most Garmin handhelds, the "custom map" (.kmz) format will only permit a map that is 10240 x 10240 feet using 1-foot imagery. That's slightly less than 2 miles x 2 miles. Using 4-foot imagery you could cover an area about 8 miles x 8 miles. You can do the math yourself for other resolutions, just multiply 10240 times the resolution in feet.

Although I haven't used it myself, I believe one nice feature about mapc2mapc is that it will help you make the best use of 100 map tiles when making custom maps, and even has a grid where you can create irregularly-shaped maps that show exactly your area of interest.

As discussed above, you can get around the 100 tile limit by using .jnx files and fooling Garmin's servers to think they are Birdseye to authorize them for your gps. That will allow you to use something like 50,000 tiles.


An important difference is that the tile limit (100/500) on KMZ files is per device (across all installed maps) whereas the 50000 limit for JNX is per map - and effectively no limit per device.


True, but actually it is rather constraining. You need an *active* Birdseye subscription to be able to use .jnx files. You then must trick Garmin's servers into believing your imagery is actually Birdseye, because it must be authorized by Garmin or it won't work on the GPS. This all works fine, but (apparently) you can only have one Birdseye map per subscription.

This becomes an issue if you want to use "real" Birdseye imagery in addition to your own. If you have them both loaded on the GPS, they will be merged together which is a mess. So you would need separate SD cards - one with your own .jnx files and another with Garmin .jnx files if you want to use both. Now, there may be some way around this but I could not find it the last time I tried.

I suppose it would be possible to have multiple active Birdseye subscriptions (such as topo and satellite) if you want to have two kinds of imagery on the GPS at the same time. Of course, none of this gets around the terrible performance of raster imagery on Garmin handhelds. It is really slow to zoom and pan the map. And the screens on my Garmin GPS'es look terrible with aerial imagery, it's a "muddy mess" on my Montana 600 and the colors are all wrong too. Garmin has optimized their screens for high-contrast vector maps, not aerial photography with subtle shades of green and brown.

Lucky Dog

Thanks for the great information.
After reading all of the responses, and studying the links and methods, I have concluded that I'm a little out of my wheelhouse and will have to do without aerial images on my Garmin devices for a while.

The reason for my post was in reaction to Garmin ending Birdseye subscriptions. The only option for Birdseye currently is with Birdseye Direct, which works on few Garmin devices.

Thanks for the very interesting posts.


Garmin is ending Birdseye? Wow, I had not heard that. Do you have any more information about this? I found these with a quick search

If this is true... then you can probably disregard everything we have posted about making your own .jnx files. If Garmin is discontinuing it in basecamp, you would not be able to authorize your home-made .jnx files and they would be useless on the GPS.  >:(