Hi Everyone,
I have what might seem to be a strange/silly question but I'm confused and need some advice.
I created a route using transDEM and am trying to model it after a real life route. Pictures are better than words, so let me explain. First, take a look at this picture:
In the mid upper left you can see brown lines going over the tracks. Note how the tracks cut into the terrain. The brown lines are roads and go over the tracks as an overpass. I can see via google earth and panorama that there is an abutment of earth to help support the bridge.
Up until now, I always tried to lay tracks on top of the DEM terrain. I guess I have several questions I should ask:
1) How is DEM data is collected? Is it the height from space from a satellite that is interpreted as numbers and then mathematically combined to give heights? Because as you can see, if I lay the tracks on top of the terrain, I'd have to raise the land more to compensate reality. That would lead to a nasty gradient that I can't see via panorama.
2) For those who use DEM's, is it normal to have to do some investigative work to know where the track should cut through the terrain and where it shouldn't? This seems logical to me because simply laying the track on top of the terrain would have a killer gradient as I mentioned before.
3) What about other factors such as traffic, trains, snow...does that lead to inaccuracies with the DEM data itself?
Now look at this picture:
If I apply the logic I deduced above and make the tracks cut through the ground, all seems well, but the ground near the overpass is gently sloped and in real life it is not:
So much so that it seems inaccurate. Does this mean I have to adjust that terrain too? There is a shopping mall here:
Which I know is on level terrain so I suppose I'll have to go about adjusting the terrain there manually right?
If so, does this mean that the rest of the data, or that data in DEMs is seriously limited? Hopefully, my questions make sense...
:wave:
Gisa ^^
I have what might seem to be a strange/silly question but I'm confused and need some advice.
I created a route using transDEM and am trying to model it after a real life route. Pictures are better than words, so let me explain. First, take a look at this picture:
In the mid upper left you can see brown lines going over the tracks. Note how the tracks cut into the terrain. The brown lines are roads and go over the tracks as an overpass. I can see via google earth and panorama that there is an abutment of earth to help support the bridge.
Up until now, I always tried to lay tracks on top of the DEM terrain. I guess I have several questions I should ask:
1) How is DEM data is collected? Is it the height from space from a satellite that is interpreted as numbers and then mathematically combined to give heights? Because as you can see, if I lay the tracks on top of the terrain, I'd have to raise the land more to compensate reality. That would lead to a nasty gradient that I can't see via panorama.
2) For those who use DEM's, is it normal to have to do some investigative work to know where the track should cut through the terrain and where it shouldn't? This seems logical to me because simply laying the track on top of the terrain would have a killer gradient as I mentioned before.
3) What about other factors such as traffic, trains, snow...does that lead to inaccuracies with the DEM data itself?
Now look at this picture:
If I apply the logic I deduced above and make the tracks cut through the ground, all seems well, but the ground near the overpass is gently sloped and in real life it is not:
So much so that it seems inaccurate. Does this mean I have to adjust that terrain too? There is a shopping mall here:
Which I know is on level terrain so I suppose I'll have to go about adjusting the terrain there manually right?
If so, does this mean that the rest of the data, or that data in DEMs is seriously limited? Hopefully, my questions make sense...
:wave:
Gisa ^^