SeeYou incorrect waypoint altitudes

soaringjac wrote on 2/2/2020 8:33 AM:
On Saturday, February 1, 2020 at 7:48:36 AM UTC-8, Eric Greenwell wrote:
soaringjac wrote on 1/31/2020 7:59 PM:
Just started using seeyou for the first time. I created some waypoints in seeyou and noticed the altitude shown for some of the waypoints are way off. I double checked the exact same point in Google earth and the difference is about 1000'. This isn't the case for all custom waypoints I made, but it is true for most of them. How are you guys creating accurate waypoints and waypoint altitudes. Kind of crazy that seeyou is so off!

For what purpose will you use the waypoints? If it's for task planning, the
correct elevation doesn't matter; if it's for potential landing places, you should
not depend on SeeYou, but on a more accurate source. SeeYou is a flight planning
tool, and it's your flight computer that needs elevation accuracy. I use official
databases as my first choice; for landing places not in the official databases, I
use databases from pilots I trust, sometimes from Google, perhaps topographic
maps. I also plan to arrive higher at those landing places, partly because the
elevation may not be known as accurately as airports on the charts.


Just adding a couple local landmarks to my S100, mainly going to use to see if I have glide to the various waypoints. Not doing any XC or competition stuff. I might try some databases but it seems a bit overkill for now. I just want a couple local landmarks.

I maybe be assuming the wrong things. What are you using as your flight computer,
and does it already have the local airports in it?

Usually, we use "landmark" for point of reference only, like a mountain peak or
bridge. By "landmarks", do you mean "places I could land safely?

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1

Post the actual waypoint data here... it’s just ASCII text. Then we have a chance of seeing what is going on.

On Sunday, February 2, 2020 at 4:12:02 PM UTC-5, Darryl Ramm wrote:
Post the actual waypoint data here... it’s just ASCII text. Then we have a chance of seeing what is going on.

Here you go. I created this waypoint about 3 minutes ago. Use whatever tool you like to correlate lat/long/elevation. Actual elevation closer to 1220m....

"Brumley Mountain",,,3650.274N,08206.228W,1091.5m,1,,,,,,

T8

On Sun, 02 Feb 2020 14:26:54 -0800, Tango Eight wrote:

On Sunday, February 2, 2020 at 4:12:02 PM UTC-5, Darryl Ramm wrote:
Post the actual waypoint data here... it’s just ASCII text. Then we
have a chance of seeing what is going on.

Here you go. I created this waypoint about 3 minutes ago. Use whatever
tool you like to correlate lat/long/elevation. Actual elevation closer
to 1220m....

"Brumley Mountain",,,3650.274N,08206.228W,1091.5m,1,,,,,,

Interesting, so I went looking with Google Earth...

That point seems to be on the side of a forested ridge at 1187m on the
Blue Mountains in VA.

A more obvious TP would be the rock outcrops at 35 50.11.9N 82 06.1492W,
or 3550.119N 08206.119W in Seeyou format, but of course ymmv.

Of course, this all assumes the OP didn't mean "Bromley Mountain", at the
top of the Bromley Ski Resort, Vermont at 996m (43 13'15.67"N 072
56'19.37W or 4313.157N 07256.1837W in SeeYou format) - which would be a
much more obvious turnpoint.


--
Martin | martin at
Gregorie | gregorie dot org

On Sunday, February 2, 2020 at 7:28:38 PM UTC-5, Martin Gregorie wrote:
On Sun, 02 Feb 2020 14:26:54 -0800, Tango Eight wrote:

On Sunday, February 2, 2020 at 4:12:02 PM UTC-5, Darryl Ramm wrote:
Post the actual waypoint data here... it’s just ASCII text. Then we
have a chance of seeing what is going on.

Here you go. I created this waypoint about 3 minutes ago. Use whatever
tool you like to correlate lat/long/elevation. Actual elevation closer
to 1220m....

"Brumley Mountain",,,3650.274N,08206.228W,1091.5m,1,,,,,,

Interesting, so I went looking with Google Earth...

That point seems to be on the side of a forested ridge at 1187m on the
Blue Mountains in VA.

A more obvious TP would be the rock outcrops at 35 50.11.9N 82 06.1492W,
or 3550.119N 08206.119W in Seeyou format, but of course ymmv.

Of course, this all assumes the OP didn't mean "Bromley Mountain", at the
top of the Bromley Ski Resort, Vermont at 996m (43 13'15.67"N 072
56'19.37W or 4313.157N 07256.1837W in SeeYou format) - which would be a
much more obvious turnpoint.


--
Martin | martin at
Gregorie | gregorie dot org

It's a ridge route. If you've done any flying of that sort, it'll make sense. If you haven't... look at the the topo and do the thought experiment.

https://viewer.nationalmap.gov/basic...vail=&refpoly=

T8

On Sun, 02 Feb 2020 16:52:59 -0800, Tango Eight wrote:

It's a ridge route. If you've done any flying of that sort, it'll make
sense. If you haven't... look at the the topo and do the thought
experiment.

Very little, and that was on steeper, more defined ridges - the ridge
north of Omarama and on the Pennines under Cross Fell. I take your point
about marking the start of a ridge climb.

https://viewer.nationalmap.gov/basic/?
basemap=b1&category=nbd,ned,nedsrc,histtopo,nhd,na ip,nbdmi,gnis,smallscale,nsd,vectorcmb,ntd,ustopo, woodland&q=&zoom=12&bbox=-82.25360870,36.76584198,-81.94805145,36.91201927&preview=&avail=&refpoly=

FWIW GoogleEarth can give rather good topographic views if you move off a
bit (1km or so) and then zoom right in, almost to the point where it
wants to switch to streetview. Then moving your viewpoint around lets you
easily pick out high points, ridgelines, etc.


--
Martin | martin at
Gregorie | gregorie dot org

On Sunday, February 2, 2020 at 5:26:56 PM UTC-5, Tango Eight wrote:
On Sunday, February 2, 2020 at 4:12:02 PM UTC-5, Darryl Ramm wrote:
Post the actual waypoint data here... it’s just ASCII text. Then we have a chance of seeing what is going on.

Here you go. I created this waypoint about 3 minutes ago. Use whatever tool you like to correlate lat/long/elevation. Actual elevation closer to 1220m....

"Brumley Mountain",,,3650.274N,08206.228W,1091.5m,1,,,,,,

T8

The elevation data built into the map that is within SeeYou is only approximate, as it is presumably based on a "grid elevation model" with limited resolution. The more varied (mountaneous) the local topography, the more inaccurate it would be, since those grid points are farther apart than the actual local slopes. I always enter waypoint elevations "manually", from other sources.

On Sunday, February 2, 2020 at 5:35:27 PM UTC-8, wrote:
On Sunday, February 2, 2020 at 5:26:56 PM UTC-5, Tango Eight wrote:
On Sunday, February 2, 2020 at 4:12:02 PM UTC-5, Darryl Ramm wrote:
Post the actual waypoint data here... it’s just ASCII text. Then we have a chance of seeing what is going on.

Here you go. I created this waypoint about 3 minutes ago. Use whatever tool you like to correlate lat/long/elevation. Actual elevation closer to 1220m....

"Brumley Mountain",,,3650.274N,08206.228W,1091.5m,1,,,,,,

T8

The elevation data built into the map that is within SeeYou is only approximate, as it is presumably based on a "grid elevation model" with limited resolution. The more varied (mountaneous) the local topography, the more inaccurate it would be, since those grid points are farther apart than the actual local slopes. I always enter waypoint elevations "manually", from other sources.



Cool thanks, that's basically the answer i thought i would get. Pretty much "enter your elevations manually"

On Sunday, February 2, 2020 at 2:26:56 PM UTC-8, Tango Eight wrote:
On Sunday, February 2, 2020 at 4:12:02 PM UTC-5, Darryl Ramm wrote:
Post the actual waypoint data here... it’s just ASCII text. Then we have a chance of seeing what is going on.

Here you go. I created this waypoint about 3 minutes ago. Use whatever tool you like to correlate lat/long/elevation. Actual elevation closer to 1220m....

"Brumley Mountain",,,3650.274N,08206.228W,1091.5m,1,,,,,,

T8

Hi Evan. I was not really asking you for a waypoint. We already discussed this, I hope we both understand why mountainous terrain elevations are likely to not be accurate/disagree like this. I was asking the OP for the waypoints *he* is having problems with. (I see we have a waypoint now, I'll look at that next).

If they are not near vertical discontinuities, or deep vegetation, then differences might be expected. Otherwise maybe it's somethingÂ*corruptedÂ*in his SeeYou, or some bad data in that area, or... and if so something Naviter support should see.

But for those playing along at home. ThatÂ*Brumley Mountain waypoint as already pointed out is hanging off a fairly steep side of the mountain I it should not be a surprise that SeeYou and Google Earth or pick any other (random tools) produce different data. You have to think about where the data comes from and what it is showing.

For the USA I believe Google Maps and Google Earth uses USGS DEMS high resolution LIDAR data sets, with few m lateral resolution. SeeYou used to use the ~global 30m (or 60m?) lateral resolution NASA Shuttle C-band Synthetic Aperture Radar datasets with global coverage, and I suspect they still do, I'd be surprised if Naviter added DEMS data for the USA. (Who wants to buy Andrej beer at the SSA convention to try to get DEMS support for the USA?)

I expect resolution effects here of scale 30m/60m laterally can significantly affect reported altitudes. And when working in SeeYou on Windows you also want to be careful because some of the charts do not resolve sharp features well and it might be possible to place stuff a bit off. But the other critical question is likely vegetation. Do you want to count elevation of the ground surface or of the top of forrest vegetation? What do the software programs and their data sources mean by elevation? The answer there is probably "uh?" :-) The LIDAR data is affected by vegetation more than the C-band data but they try to factor out vegetation, by that may not alway be accurate. (Folks actually measure forrest heights from the difference of LIDAR and C-Band SAR). So where this is critical you better be clear what you mean, and find a way to validate you have an accurate elevation..

For thatÂ*Â*Brumley Mountain waypoint

3,887'Â* Â*Google EarthÂ*7.3.2.5776 (Mac):
3,581'Â* SeeYou (Windows) 10.32Â* Â* Â* Â* Â* :
-----
306' difference
-----

It takes displacing the google Earth waypoint about 180m laterally "down hill" to reach that reported SeeYou elevation. That's not unreasonable given the 30/60 meter resolution, and possible vegetation effects would mean less displacement is needed.

If I drop a way point more up on that flat top of the hill at N36°50.220' W082°05.696'. Google Earth and See You agree more.

3994'Â* Â*Google EarthÂ*7.3.2.5776 (Mac)
3855'Â* Â*SeeYou (Windows) 10.32
-----
139' difference.Â*
-----

I am going to guess a good part of that of that is vegetation effect.Â*

The counter example is to pick locations that have no vegetation and are roughly flat at few x 30m/60m scale and compare them. The easy pick there is airport runways. When I compare the runway intersection at Patrick AFB, FL I get 6 or so feetÂ*+/- few feet. OK that's sea level, so going higher, the runway intersection at Cedar City Airport, UT is 5,999Â*+/- a few feet in either tool. Pretty amazing precision. (Ah memories of irritating a Cedar City tower controller one day and him making me push my DG-303 all the to the end of Runway 8, in the stinking heat. Grrr).

Anyhow precision altitude alway needs to be hand curated, it's great when that is well done. Like when boulder outcrops or mountain top forestry fire lookouts are within feet of the shown elevation on the altimeter. Landing locations are usually relatively easy.

On Sunday, February 2, 2020 at 9:11:49 PM UTC-5, Darryl Ramm wrote:
On Sunday, February 2, 2020 at 2:26:56 PM UTC-8, Tango Eight wrote:
On Sunday, February 2, 2020 at 4:12:02 PM UTC-5, Darryl Ramm wrote:
Post the actual waypoint data here... it’s just ASCII text. Then we have a chance of seeing what is going on.

Here you go. I created this waypoint about 3 minutes ago. Use whatever tool you like to correlate lat/long/elevation. Actual elevation closer to 1220m....

"Brumley Mountain",,,3650.274N,08206.228W,1091.5m,1,,,,,,

T8

Hi Evan. I was not really asking you for a waypoint. We already discussed this, I hope we both understand why mountainous terrain elevations are likely to not be accurate/disagree like this. I was asking the OP for the waypoints *he* is having problems with. (I see we have a waypoint now, I'll look at that next).

If they are not near vertical discontinuities, or deep vegetation, then differences might be expected. Otherwise maybe it's somethingÂ*corruptedÂ*in his SeeYou, or some bad data in that area, or... and if so something Naviter support should see.

But for those playing along at home. ThatÂ*Brumley Mountain waypoint as already pointed out is hanging off a fairly steep side of the mountain I it should not be a surprise that SeeYou and Google Earth or pick any other (random tools) produce different data. You have to think about where the data comes from and what it is showing.

For the USA I believe Google Maps and Google Earth uses USGS DEMS high resolution LIDAR data sets, with few m lateral resolution. SeeYou used to use the ~global 30m (or 60m?) lateral resolution NASA Shuttle C-band Synthetic Aperture Radar datasets with global coverage, and I suspect they still do, I'd be surprised if Naviter added DEMS data for the USA. (Who wants to buy Andrej beer at the SSA convention to try to get DEMS support for the USA?)

I expect resolution effects here of scale 30m/60m laterally can significantly affect reported altitudes. And when working in SeeYou on Windows you also want to be careful because some of the charts do not resolve sharp features well and it might be possible to place stuff a bit off. But the other critical question is likely vegetation. Do you want to count elevation of the ground surface or of the top of forrest vegetation? What do the software programs and their data sources mean by elevation? The answer there is probably "uh?" :-) The LIDAR data is affected by vegetation more than the C-band data but they try to factor out vegetation, by that may not alway be accurate. (Folks actually measure forrest heights from the difference of LIDAR and C-Band SAR). So where this is critical you better be clear what you mean, and find a way to validate you have an accurate elevation..

For thatÂ*Â*Brumley Mountain waypoint

3,887'Â* Â*Google EarthÂ*7.3.2.5776 (Mac):
3,581'Â* SeeYou (Windows) 10.32Â* Â* Â* Â* Â* :
-----
306' difference
-----

It takes displacing the google Earth waypoint about 180m laterally "down hill" to reach that reported SeeYou elevation. That's not unreasonable given the 30/60 meter resolution, and possible vegetation effects would mean less displacement is needed.

If I drop a way point more up on that flat top of the hill at N36°50..220' W082°05.696'. Google Earth and See You agree more.

3994'Â* Â*Google EarthÂ*7.3.2.5776 (Mac)
3855'Â* Â*SeeYou (Windows) 10.32
-----
139' difference.Â*
-----

I am going to guess a good part of that of that is vegetation effect.Â*

The counter example is to pick locations that have no vegetation and are roughly flat at few x 30m/60m scale and compare them. The easy pick there is airport runways. When I compare the runway intersection at Patrick AFB, FL I get 6 or so feetÂ*+/- few feet. OK that's sea level, so going higher, the runway intersection at Cedar City Airport, UT is 5,999Â*+/- a few feet in either tool. Pretty amazing precision. (Ah memories of irritating a Cedar City tower controller one day and him making me push my DG-303 all the to the end of Runway 8, in the stinking heat. Grrr).

Anyhow precision altitude alway needs to be hand curated, it's great when that is well done. Like when boulder outcrops or mountain top forestry fire lookouts are within feet of the shown elevation on the altimeter. Landing locations are usually relatively easy.

Excuses, excuses! This worked much better at about version 4. That was my point. The elevation data served by the SeeYou cloud is relative crap. Very coarse. Probably a good decision on Naviter's part. "Hey, we can save a ton of money on bandwidth, only a couple of ridge soaring pilots will ever notice.
If they do complain, we can probably rely on their buddies to tell them they are being too demanding" :-).

best,
Evan