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Arden
06-07-2015, 14:55
Hi;
I downloaded the 39 .kmz files, which make up the entire AT, in Google Earth. I have created image overlays for some of the parks I have hiked (Nj and NY mainly). What I have done is scanned the maps (NY/NJ TC) and cropped as necessary, then lined up the roads, lakes, etc on the images with the real images in Google Earth. Now I've got an overlay that shows trails.
When I look at these overlays, there is quite a discrepancy between where the trail maps show the AT compared to where the .kmz files I downloaded show it, and where Google Earth places the trail.
I have always accepted the NY/NJ Trail Conference maps as the most accurate, but how can I be sure?

It's not all that important, except for getting to the trailheads, but I am in the process of creating trail maps that I can use on my Android phone while hiking. I have purchased one of the North Jersey maps from NY/NJ TC as PDF maps from Avenza. The maps look great and appear very accurate when you have a good GPS signal.
But not all of the AT is available in this format, so I am trying to create my own with Google Earth and my paper maps.

Thanks for your help/advice

Arden

Arden
06-07-2015, 15:10
Update:
On the ATC website, I found the .kml file to download. Interestingly, this data has the trail following the Google Earth position fairly closely in some areas, and the NY/NJ TC maps position in others.
I am going to use the data from ATC, since it was obtained from National Parks.

Buttercup01
06-09-2015, 01:33
Keep looking. I found a .gpx with the complete center line that was correctly joined. The AT conference centerline is not joined and is useless without editing. Yes, the AT as shown on most topo's will differ from the actual centerline. The best way to prove it is to hike the trail.

Arden
06-09-2015, 10:03
the kml (or kmz) is actually what I was looking for. This is what I downloaded from the NPS website. I only wish that I could import the kml/kmz files to my android phone with Google Earth, but so far I don't see an option to do so.
Regardless; I would not do any major hiking on the AT without a set of paper (tyvec) maps. I have found that in many locations, GPS is unreliable, and using the phone a lot uses up battery power.
What I would really like to do is use the Google Earth maps with the kml file for the AT, and create a 3-D rendition of the entire trail.
I actually have the tools to do this; only need the motivation and the time.

Arden

backpacker451
06-09-2015, 13:18
I have about 5 Hi-res GPX files of the trail by state. They are pretty spot on where I tested them. For example, for Vermont, it has 15490 points for 150 miles. If you want to try one, I think I can attach it here.

Another Kevin
06-09-2015, 16:13
It's not all that important, except for getting to the trailheads, but I am in the process of creating trail maps that I can use on my Android phone while hiking. I have purchased one of the North Jersey maps from NY/NJ TC as PDF maps from Avenza. The maps look great and appear very accurate when you have a good GPS signal.
But not all of the AT is available in this format, so I am trying to create my own with Google Earth and my paper maps.

What Android app are you using? (I happen to use Backcountry Navigator.) Will it let you point at a custom source for map tiles? If so, I may be a little bit farther along than you are, and be able to share insight, or maybe even maps.

I've been playing around with making my own maps for a while now. I have a "proof of concept" previewer (http://kbk.is-a-geek.net/catskills/test.html?la=41.244&lo=-74.198&z=13) up on my web site, and I've worked out how to download pieces to my phone. (I don't have the bandwidth to support a lot of usage, so if others are going to start picking it up, we need to work out how to host it.) You can play around with panning and zooming to look where you want. (I just started it near the NY/NJ section, since you mentioned the NYNJTC maps.) The entire A-T should be on it. Don't get fooled by the 'catskills' moniker - this started out a Catskill project but got entirely out of hand.

As far as smartphone maps that you can buy, you might want to check out Guthook's app (http://www.guthookhikes.com/apps). He's farther along than I am, although I have reasons for preferring my own map (mostly just that it suits me!).

bemental
06-09-2015, 20:43
the kml (or kmz) is actually what I was looking for. This is what I downloaded from the NPS website. I only wish that I could import the kml/kmz files to my android phone with Google Earth, but so far I don't see an option to do so.
Regardless; I would not do any major hiking on the AT without a set of paper (tyvec) maps. I have found that in many locations, GPS is unreliable, and using the phone a lot uses up battery power.
What I would really like to do is use the Google Earth maps with the kml file for the AT, and create a 3-D rendition of the entire trail.
I actually have the tools to do this; only need the motivation and the time.

Arden

Try researching a different Android mapping app. I found a few on iOS that allowed me to import a KML/KMZ and load system, or custom map tiles.

Worked very well, but on iOS the Google Earth app is mainly just a toy, too.

scrabbler
06-09-2015, 20:50
Not quite what you asked, but maybe a better option - use a Garmin GPS with mapping features. Here's all the free & accurate maps you could ever desire.

http://www.gpsfiledepot.com/maps/state/all

iAmKrzys
06-09-2015, 22:37
I think almost entire length of AT is mapped on https://www.openstreetmap.org/. You can download gpx for AT from http://waymarkedtrails.org/en/relation/156553#routes that is built using OSM data.

I am not surprised that scanning NYNJTC map and creating an overlay in Google Earth did not produce perfect results - I have converted a number of PDF maps to .kmz files for use on my Garmin eTrex 30 and it is often really tricky to find a good combination of scale and rotation to match all the landmarks. There is also an issue of projection - there are lots of ways to project Earth's round surface onto a plane (i.e. piece of paper.) Additionally, you may also have some distortion while scanning that would not be easy to correct for. Finally, satellite imagery in Google Earth may not be perfect.

I bet that none of the digital data sets that you have access to comes for a survey-grade equipment and regular gps units have limited accuracy so any of these gpx files will be perfectly fine for hiking but not good enough to record in a deed.

If you are using Android phone than you may take a look at OsmAnd+ (my favorite) that allows you to download OSM maps for off-line use and it also support contour lines via a plug-in. OsmAnd maps get updated monthly.

lilricky
06-21-2015, 19:20
I have a heck of a time connecting the various tracks on the ATC's site everytime there's a reroute, but its a labor of love :) check out http://www.lilricky.com and download the .gpx for the AT. I recommend using Garmin's Basecamp software and the free topo software at gpsfiledepot.com You can use the software to print or display the AT track even without a GPS.

postholer.com
06-24-2015, 12:15
Any trail on Google Earth should be suspect. None of the traces that I have, and most are very accurate, match up with google earth. You can make comparisons with a number of trails on this google map. (http://postholer.com/gmap/gmap.php?trail_id=1) The same can be said for DeLorme maps.

Get gpsbabel. It is free and you can easily convert from format to format to your hearts desire. Use it at the command line or GUI.

Cleaning up kml's is fun and easy. Back in 2007 the ATC centerline kml consisted of 4,000 linestring segments, yes 4,000! The thought of cleaning that up was nauseating. I had other messy kml's as well that I dealt with.

So I created geoLineString. It's a php class used to order, truncate, append, get 2D/3D distances/elevations, add/remove segments, convert to .csv and generally work on collections of 'LineStrings'. This is the first tool any new kml gets parsed by. I've been using/upgrading/tweaking it for the last 7 years. I almost released it to the public earlier this year, but I couldn't bring myself to do it. It gives me a huge advantage in time and resource saving.

-postholer

Another Kevin
06-24-2015, 15:17
When I'm making maps for my own use, I often draw on multiple data sources. For instance, for the A-T in southwestern Massachusetts, I have the centerline from ATC, the trails from MassGIS, OpenStreetMap, and my own GPS tracks.

None is correct.

What I've taken to doing on maps that I produce for myself is showing all of them, perhaps rendered differently. That sometimes gives the map a bit of a "cubist" appearance where it renders the same trail with different routings, as with the A-T on Mount Everett (http://kbk.is-a-geek.net/catskills/karl.html?la=42.1022&lo=-73.4318&z=15). When I see a tangled braid on the map, I know it has several common possible causes.

the trail was rerouted between the times that different mappers gathered the data. (They swung the trail farther toward the cliff edge for the view, after the fire tower was taken down.)
the trail is ambiguous, paralleled by herd paths, or difficult to follow, and different mappers took different paths. (The old trail is still there, and it's easy to miss the new switchback,. In fact, I snowshoed right past it once without noticing.)
there's a geographic feature, like a slot canyon, that makes GPS go wonky, so different people on the same trail get different tracks.
some agency did something like trace over a paper map at an inappropriately large scale.

plus a few less likely things. In any case, these are warning signs that the trail may be confusing or difficult to follow and I need to keep my eyes open and perhaps allow extra time.

For this reason, on the maps I make for myself, I don't even try to reduce trails to a single authoritiative "the trail is here." Trails in the field are like that, too, particularly ones that aren't superhighways like the A-T. They're confusing, uncertain, have local reroutes or unclear sections, peter out into brush or blowdown that has to be whacked around, get wiped out by beavers, and so on. They're approximate things.

rocketsocks
06-24-2015, 15:47
When I'm making maps for my own use, I often draw on multiple data sources. For instance, for the A-T in southwestern Massachusetts, I have the centerline from ATC, the trails from MassGIS, OpenStreetMap, and my own GPS tracks.

None is correct.

What I've taken to doing on maps that I produce for myself is showing all of them, perhaps rendered differently. That sometimes gives the map a bit of a "cubist" appearance where it renders the same trail with different routings, as with the A-T on Mount Everett (http://kbk.is-a-geek.net/catskills/karl.html?la=42.1022&lo=-73.4318&z=15). When I see a tangled braid on the map, I know it has several common possible causes.

the trail was rerouted between the times that different mappers gathered the data. (They swung the trail farther toward the cliff edge for the view, after the fire tower was taken down.)
the trail is ambiguous, paralleled by herd paths, or difficult to follow, and different mappers took different paths. (The old trail is still there, and it's easy to miss the new switchback,. In fact, I snowshoed right past it once without noticing.)
there's a geographic feature, like a slot canyon, that makes GPS go wonky, so different people on the same trail get different tracks.
some agency did something like trace over a paper map at an inappropriately large scale.

plus a few less likely things. In any case, these are warning signs that the trail may be confusing or difficult to follow and I need to keep my eyes open and perhaps allow extra time.

For this reason, on the maps I make for myself, I don't even try to reduce trails to a single authoritiative "the trail is here." Trails in the field are like that, too, particularly ones that aren't superhighways like the A-T. They're confusing, uncertain, have local reroutes or unclear sections, peter out into brush or blowdown that has to be whacked around, get wiped out by beavers, and so on. They're approximate things.
Beautiful maps...thanks to all.