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General Discussion / Re: Create LIDAR overlay
« Last post by Boyd on October 16, 2019, 07:26:33 AM »
Why were you not able to transfer it? Connect the GPS to your computer and open the Garmin folder. If necessary, create a folder named CustomMaps. Copy the Google Earth .kmz file to that folder.

You must use .jpg images for the .kmz, it will not work with .png images. Make sure that the image you created is no larger than 1024 x 1024 pixels. Also, only use letters and numbers in the filename. There's an old bug where a file named my_map.kmz would not work but mymap.kmz does work. This may have been fixed though, not sure.

I assume you already know where to find the LIDAR imagery, since you're already using it? If it has 1-meter resolution, then each map tile can be about 1km x 1km (1024m x 1024m). You can use 100 of these tiles at the same time.

For more versatility, you would download the actual DEM files from the USGS, then use some software to render them in whatever style you like. Sounds like MojaveMan has some ideas for this. I use GlobalMapper, which makes all of this trivial, and it can directly create the Garmin custom maps. It is expensive software however.

Again, look at the other thread i linked to: https://forums.gpsfiledepot.com/index.php?topic=4556.0

As discussed there, qGIS and mapc2mapc are useful tools for this. qGIS is free, open source software Mapc2mapc is not free however. g-raster is also mentioned in that thread, and is another tool that is worth a look. Again, it is not free.

General Discussion / Re: Create LIDAR overlay
« Last post by syncro on October 16, 2019, 07:11:38 AM »
Just catching up and a lot of great discussion, thank you. I dont think I cant respond to all of it but I certainly read all of it and appreciate the input.

I am interested in a custom map with fairly high resolution (able to detect features around 1-3 meters in size). The size of the map would cover maybe a square mile (or a few smaller ones) and the most important feature is the ability to view the map on my handheld GPS. Currently, I use LiDAR to pick points of interest and grab the GPS location of that feature and log it into excel. I then load that spreadsheet into a google map then save that file as a KML that then gets transferred to my device. When I am in the field, I am able to locate the POI just fine, but then have hard copy print outs of the LiDAR for reference...its not all that great bouncing between GPS topo lines and hardcopy LiDAR print outs.

As a response to the first reply in the thread, I was able to play around with google earth pro enough to do a decent overlay. It took a few trys but I was able to line up almost all features with my pins, however, I cannot transfer the overlay to my device.
General Discussion / Re: Convert a Garmin img file to GPX
« Last post by Red90 on October 15, 2019, 07:01:25 PM »
General Discussion / Convert a Garmin img file to GPX
« Last post by wtrskinut1 on October 15, 2019, 01:32:03 PM »
I am sure this is easy for someone with the knowledge. I am having a hard time figuring out how to convert the img file that is created on map installs to a gpx or other format. or maybe it is not possible.

Thanks in advance
General Discussion / Re: Create LIDAR overlay
« Last post by Boyd on October 15, 2019, 10:24:46 AM »
LOL, nothing to "disclose" there, it's available from the National Map, just like other elevation products. If available, you'll see 1-meter DEM listed in a search.


FInding coverage areas is frustrating on their site. They often show big polygons of available data, but when you look at the downloads, only a little corner of that area is actually covered.

But I think there are large parts of the US (maybe even the majority of it?) with no high res LIDAR data available at all (neither 1/9 arc-second nor 1-meter). Fortunately, there is very good coverage of my small state of NJ, and it's more than enough to keep me busy making maps. :)
General Discussion / Re: Create LIDAR overlay
« Last post by MojaveMan on October 15, 2019, 09:55:38 AM »
Can you disclose your source for your 1 meter data, and about how much of the country is covered?
General Discussion / Re: Create LIDAR overlay
« Last post by Boyd on October 15, 2019, 09:18:57 AM »
I'm attaching an extreme close-up of the shaded topo I posted above.indicates.

FWIW, here is an example of 1-meter LIDAR at full resolution


This view would be equivalent to the resolution of 1/3 arc-second data (although it was created by down-sampling the hi-res imagery)


The 1-meter LIDAR is especially interesting in my flat, coastal area because it reveals things you won't find on topo maps or aerial imagery, such as overgrown cellar-holes of old structures. You can see some examples in the beta version of the new software I'm writing:

General Discussion / Re: Create LIDAR overlay
« Last post by MojaveMan on October 15, 2019, 09:13:23 AM »
Anyway, back to syncro - do you think a custom map here will meet your needs?  Do you think this resolution is too poor?

As I mentioned in an edit to my last post, by sheer coincidence, its about 1 pixel per meter.  BUT, its based on 1/3 arc second, and nothing I am doing is really improving on that original resolution beyond a simple resize.
General Discussion / Re: Create LIDAR overlay
« Last post by Boyd on October 15, 2019, 09:05:59 AM »
Seems like the key to that is the disclaimer "when produced". But, really, I don't know. In the past 1/3 arc-second data was certainly not LIDAR. Maybe they are upgrading it? Regardless, 1/3 arc-second is very low resolution, about 30 feet per pixel. That will only be useful for providing a general idea of terrain at low zoom levels. It will not reveal interesting surface detail when you zoom way in.

But if that suits your needs.... nothing wrong with it. :)
General Discussion / Re: Create LIDAR overlay
« Last post by MojaveMan on October 15, 2019, 08:44:52 AM »
Did not see anything indicating the 1/3 arc-second data is LIDAR-derived.

The 1/3 arc-second data is discussed in the "Seamless" section, which is part of the "Standard DEMs".  If you read the section about the Standard Dems you will see:
"Seamless DEMs are produced by blending only the highest quality project data into a continuous terrain surface for the U.S."

And what is "Project Data"?
" Project-based DEMs are available for the full areal extents of projects when produced from light detection and ranging (lidar), or as one-degree blocks with overedge when produced from IfSAR."

I'm attaching an extreme close-up of the shaded topo I posted above.  If the shade was based on the topo data, I don't think the detail that exists in the shade would be there...and when I put this image into google earth, there is, indeed, a knob there in the terrain just as the shade indicates.

By *sheer* coincidence, that shade is about 1 pixel per meter.  I pulled it up in Google Earth, and that knob is about 57 meters across - and the pixel count is about 33 across by 47 tall.
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