WIP how to use Google Earth to find precise altitude data for the road surface

Karu62 · Jun 5, 2013

greetings. im not shure, but i think most of us know about the Google Earth altitude data mismatch when importing to BTB. i had downloaded Hybrid Geotools ( a Google Earth plugin) to layout a track and give it altitude data when i found the problem. seems the auto-update is based on sattelite data,which is not accurate.

however, if you set a Geopoint in sattelite view, then zoom in to street view, you can manipulate the Geopoint with the arrow buttons. when the Geopoint intersects with a solid object in the image, like a road or building, it will begin to dissapear into image. if you move the Geopoint so it barely touches the image (set movement to 0.01m/click),then set the "fixed" button,the Geopoint will turn into a red circle with a "+" crosshair perfectly set on the line (horizontal if setting on the road) and give you a coordinance with 0.01m accuracy. this data isnt from the sattelite, this data comes from the Google van recording the street view and is GPS data, not sattelite.

when i layout a road in BTB, i increase the cross-section from 4 to 8 tiles wide,giving me 9 points to adjust to give the road increased texture.

in the Geotools/street view, i set 9 Geopoints across the width of the road to make a cross-section measuring tool,plus 1 more Geopoint set at the other points shaping the curves gives you a linear distance measurement.

here is an example of Geopoint data i made from a test road. i took measurements at 2.5 meter intervals.

# = cross-section number
440= center of road
441=left side of road
448=right side of road
distance to (0.84) is the width between cross-section Geopoints
alt (266.29) is the altitude above sealevel,generated by the Google van and imprinted into the image data
distance= linear distance down the road
all measurements are in meters

CROSS-SECTION - 441 - 442 - 443 - 444 - 440 - 445 - 446 - 447 - 448 -
/DISTANCE -ALT/DISTANCE TO-
# 0 /0.0 - 266.29/0.84 - 266.27/0.84 - 266.25/0.84 - 266.21/1.68 - 266.20/3.36 - 266.18/0.84 - 266.15/0.84 - 266.12/0.84 - 266.10/0.00 -
# 1 /2.50 - 266.31/0.84 - 266.29/0.84 - 266.29.0.84 - 266.27/1.68 - 266.23/3.36 - 266.24/0.84 - 266.22/0.84 - 266.20/0.84 - 266.19/0.00 -
# 2 /5.00 - 266.48/0.84 - 266.46/0.84 - 266.46/0.84 - 266.44/1.68 - 266.42/3.36 - 266.41/0.84 - 266.39/0.84 - 266.37/0.84 - 266.36/0.84 -
# 3 /7.50 - 266.53/0.84 - 266.53/0.84 - 266.51/0.84 - 266.51/1.68 - 266.49/3.36 - 266.49/0.84 - 266.47/0.84 - 266.46/0.84 - 266.45/0.84 -
# 4 /10.0 - 267.03/0.84 - 267.03/0.84 - 267.02/0.84 - 267.01/1.68 - 267.02/3.36 - 267.01/0.84 - 267.00/0.84 - 266.99/0.84 - 266.98/0.84 -
# 5 /12.5 - 267.10/0.84 - 267.10/0.84 - 267.09/0.84 - 267.08/1.68 - 267.09/3.36 - 267.07/0.84 - 267.07/0.84 - 267.06/0.84 - 267.05/0.84 -
# 6 /15.0 - 267.17/0.84 - 267.17/0.84 - 267.16/0.84 - 267.15/1.68 - 267.15/3.36 - 267.14/0.84 - 267.12/0.84 - 267.12/0.84 - 267.12/0.84 -
# 7 /17.5 - 267.22/0.84 - 267.21/0.84 - 267.22/0.84 - 267.21/1.68 - 267.18/3.36 - 267.17/0.84 - 267.15/0.84 - 267.14/0.84 - 267.14/0.84 -
# 8 /20.0 - 267.77/0.84 - 267.77/0.84 - 267.77/0.84 - 267.76/1.68 - 267.77/3.36 - 267.76/0.84 - 267.75/0.84 - 267.75/0.84 - 267.75/0.84 -
# 9 /22.5 - 267.84/0.87 - 267.83/0.87 - 267.83/0.87 - 267.81/1.74 - 267.81/3.48 - 267.81/0.87 - 267.79/0.87 - 267.79/0.87 - 267.79/0.87 -
# 10 /25.0 - 267.91/0.87 - 267.89/0.87 - 267.89/0.87 - 267.89/1.74 - 267.88/3.48 - 267.87/0.87 - 267.87/0.87 - 267.85/0.87 - 267.85/0.87 -

you can see there is alot of variation in the data.

the first 438 Geopoints were used to layout the shape of the road,disregarding altitude changes and focusing on the curves,layed out in the sattelite view.Geopoint #439 follows these points to give you an accurate straight-line measurement with #440 (the centerline Geopoint).

the altitude data is then changed manually in BTB from the 4-screen view and moving the points to the corresponding altitude from either of the 2 lower screens.

very tediouse but extremely accurate.

Barbje_Keller · Jun 6, 2013

Thanks but this is offtopic!
This info mey better place there: http://simtrackipedia.wikidot.com/home

Mangoletsi · Jun 6, 2013

This is a very confusing post to read.

It's saying the altitude/elevation data is mismatched/wrong when you import it into BTB, and this method is more accurate. Then reading all the way through to the end of the post, it says the method ignores altitude/elevation data and you have to manually input the data in yourself afterwards.

Something must be lost in translation as I understand the method, but how BTB is able to read/import this new format of data, is unclear.

Karu62 · Jun 6, 2013

its not importing it, not the cross-section anyway. after i lay out the first 438 points,i import that into BTB to make the basic layout of the track. its after that i go back and fill in the cross-section data manually. i wish there was another way to import the Google van data automatically, but i dont of any way to do that. all i know is the street scene altitude data is different from the auto-fill data,which is sattelite data.