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Messages - MojaveMan

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1
General Discussion / Re: Create LIDAR overlay
« on: October 18, 2019, 11:03:32 AM »
So, I did a little bit of math to see how much area my maps are covering, and how many tiles they take.

A USGS topo map for the Big Bend area covers about 60 square miles, and takes 4981x5682 pixels (I converted the PDF to a .png at 250 dpi with imagemagick to get these pixel counts).  That will be 5x6 tiles of 996x947 pixels each, right?  Thats a total of 30 "tiles" of the 500 my Oregon 600 can use.  I could fit 16 such maps on my Oregon (really a bit more), for a total of 960 square miles, or an area almost 31x31 miles.  That isn't bad.
For the units that allow 100 tiles, that could still take 192 square miles, or an area about 14x14 miles.  Still not too shabby, and plenty big for a camping trip.
Note this is NOT the resolution I used for the map I posted above where my measurements indicated about 1 pixel per meter.  That is a map at 600 dpi.  If I were to use a map at that resolution, they would take about 6 times as much space ("only" about 200 square miles in those 500 tiles the Oregon allows me).  But the 250 dpi is really quite adequate for the Garmin's display...the USGS Topo maps are clear at that resolution, and the shade images I generate show nice details not present in the topo map itself...it all comes together quite nicely.
Given I tend to only concentrate my trips in much smaller areas, I can load up several topo maps for many different locations before ever having to worry about running out of space.

2
General Discussion / Re: Create LIDAR overlay
« on: October 16, 2019, 09:39:07 AM »
I would be happy to walk you through my process, if you would like.

You will need:

GRASS GIS: free open source fully capable GIS
https://grass.osgeo.org/

Imagemagick - open source image manipulation software
https://imagemagick.org/

A DEM from the USGS.

If you would like me to walk you through my process, let me know and I'd be happy to go step by step with you either in these forums or via email.  Or, if you would like, just gimme some idea of the geographic area and I will give it a go to show you what an end-product can look like.

If you need help getting your .kml file into your Garmin, I'm happy to help with that, too.
First, did you use a .jpg for the image?
Second, how big is it in terms of pixels?  If its larger than 1024x1024 pixels, you have to cut it up into smaller pieces - a process called "tiling" it (cutting it up into square tiles).

3
General Discussion / Re: Create LIDAR overlay
« 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?

4
General Discussion / Re: Create LIDAR overlay
« 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.

5
General Discussion / Re: Create LIDAR overlay
« 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.

6
General Discussion / Re: Create LIDAR overlay
« on: October 15, 2019, 08:30:04 AM »
According to this page:
https://www.usgs.gov/core-science-systems/ngp/3dep/about-3dep-products-services

the data set I am using is generated using either LIDAR or lsFAR.  Unless I am misunderstanding what they are saying.  Looking at my shaded topo, you can see many areas with details that are not reflected in the topo data at all - so I highly doubt the shade data was generated from the topo data.

Your math does hold, except for one thing:  I can resize the files very easily and cover much larger areas with much smaller data.  It really depends on the resolution you require...and as I have pointed out in past posts regaring Custom Maps, you don't have to put every custom map on the Garmin all at once.  When I go to Big Bend, I load up my Big Bend maps.  When I go to somewhere else, I just load those maps.  Its not like I can cover a very large area in one trip....for something like the PCT, I could easily carry multiple microSD cards.
For my purposes, I think the data I use is more then adequate.  I am able to massage the data quite a bit and what you see in those images is higher resolution than the original 1/3 arc-second.  I have tried the 1/9 arc-second for some maps, but it isn't available everywhere, so I looked at what the 1/3 arc-second was providing me, was happy with that, and made it my standard around which I make my shade.  Taking a look at the topo map I posted, I think my own shade is 100 times better than their layer of shade, and provides much more detail.  At least, I'm very happy with those results...and I am my own customer :)


But it does beg the question - what form of output are you looking for, syncro?  Will a custom map suffice?  I have to wonder if there isn't some way of turning this into a format more readily consumable by the Garmin as some sort of transparency layer....

7
General Discussion / Re: Create LIDAR overlay
« on: October 15, 2019, 07:56:48 AM »
Yes, I end up with something that looks just like that (I think...).  I make a shade file by loading the DEM data into GRASS GIS, and telling it to project the sun in 3 different directions.  I then merge the three different shade files to create something like the attached - a shade file for the Solatario in Texas.

That technique was borrowed from this PDF:
https://pubs.usgs.gov/of/2012/1171/pdf/usgs_of2012-1171-Gantenbein_p101-106.pdf

I download that data from the USGS National Map Viewer:
https://viewer.nationalmap.gov/basic/

The data product that I use for GRASS GIS is the "1/3 arc-second DEM" in .img format.  If you would like to pick a specific area of interest I'd be happy to walk you through my process...

8
General Discussion / Re: Create LIDAR overlay
« on: October 15, 2019, 04:58:55 AM »
By LIDAR, do you mean the DEM (elevation) data provided by the USGS?
For that, I use GRASS GIS, which is free.  If you choose to use that, I'd be happy to try to help.
I'm attaching a sample of a map I made using the DEM data and a topo map.  Is the shading what you mean by LIDAR?

9
[edit] Was looking at your OP again and you mentioned the availability of imagery that is 15,000x15,000 pixels. Those should actually be compatible with your Monterra (assuming the tile limit is 500). Those could be processed as 225 tiles at 1024x1024, so you could use two of those downloads at a time.

This is mostly true, but I wanted to mention the possibility that you could optimize the number of tiles by resizing the image.  Its possible (and highly likely) that the 15,000x15000 pixel image could be resized to be smaller (therefore taking less 1024x1024 tiles) and still look great - I make many custom maps and each one has to be considered individually through some trial and error to see if a resize looks reasonable on the device.

10
Map Making Support / Re: Ontario Atlas Map
« on: October 11, 2018, 06:40:44 AM »
I have an eTrex20 (with the buttons torn off - man, that made me mad) and an Oregon 600.  With my penchant for Custom Maps, the 500 tile limit of the 600 is really nice.
If I were on the market today, I would probably consider the newer eTrex models - maybe a 20x or a Touch25 (few buttons to tear off).  I imagine with the smartphone being so prevalent, the dedicated hand-held GPS device will be a thing of the past soon...so I might grab me one before they disappear.

11
Map Making Support / Re: Ontario Atlas Map
« on: October 10, 2018, 11:11:33 AM »
Just the GPS.  All of my efforts have the end goal of a pretty map showing up in my trusty Garmin - I'm not a fan of using a smartphone as a GPS device in the back country - or any other country, for that matter :)

12
Map Making Support / Re: Ontario Atlas Map
« on: October 09, 2018, 05:49:47 AM »
Sorry, I have no experience in using the Map web app with .kmz.  I only use Google Earth.

13
Map Making Support / Re: Ontario Atlas Map
« on: October 08, 2018, 06:45:14 AM »
I'm a little bit confused about your statement that you made a .kmz and tried to load it into Google Earth.  Generally, you *make* the .kmz with google earth.  What are you creating the .kmz with?

Is tiling required in order to break the map down into the 1024x1024 resolution for Garmin devices?

Yes, the 1024x1024 tile is a Garmin "limitation".  Garmin used to have a page detailing these limitations, but for some reason I'm having trouble pulling it up at the moment.  You could google "Garmin Custom Map limitations" to read more.

The general idea is to follow these steps:
- find a map you like
- convert the map to .jpg and into the projection that GoogleEarth likes (this is where I have spent much time and effort)
- georeference the map by creating an Image Overlay in Google Earth (generally easy if your map has control points)
- export that image overlay as a .kmz
- use a "map tiler" to cut that image into a bunch of tiles that will automatically georeference each tile for you based on the larger image
- copy that "tiled" .kmz into your CustomMaps folder

I did provide you with a tiled .kmz in this thread, if you wanted to check it out.

I did find that many tilers were hosing my carefully crafted images (adding compression artifacts to the image), so be careful.

14
Map Making Support / Re: Ontario Atlas Map
« on: October 06, 2018, 04:01:04 PM »
Don't forget, you have to "tile" the image before copying it over to your Garmin.  There are programs out there to do it for you...they tend to screw up the compression on the jpg, so be careful.
I used OKMap for this example....

15
Map Making Support / Re: Ontario Atlas Map
« on: October 06, 2018, 01:16:44 PM »
Wow. One could really go insane doing this..

One can really go insane with a map with a matching projection.
Most map images I use have a different projection, adding an entire second level of insanity.
If I knew how to add maps here, I would add my latest - a map of the Fresno area of Big Bend State Park.  Its *huge*....

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