height and image data mis-aligned in some cases

I have noticed that in some cases the height data and the landsat images are not aligned.

I downloaded the 'add-ons' 04-australia.zip and 13-machu_picchu.zip.

If I zoom into Sydney Australia and 'tilt' the camera I can see great lumps in the ocean right on the coast and some of the headlands are flat. It looks like the height and image are a kilometre or so out of alignment - I know Sydney so I can see that the 'topography looks right but the images are out of register.

Similar issue at machu picchu, if you go there and tilt the camera you can see that the river that in reality goes around the 'spur' of mountain is displayed as going up the mountain and down the other side.

Do you think it could be some config on my end?
Is there some way from me to play with some offsets somewhere?
Is the data being handed out to everyone flawed?

[cloud]

i saw this too. see this missaligned river. i guess it's about 100 m missalignment. how can this happen?



PS: try to find where it is

[Beansprout]

There's a few bugs concerning place names being misaligned too. Seems like something's wrong in the algorithm WW uses.

[TomServo]

Originally posted by TheBeansprout@Nov 4 2004, 07:16 AM
There's a few bugs concerning place names being misaligned too. Seems like something's wrong in the algorithm WW uses.

Quoted post

Chris mentioned a few times he thinks that applying a curve to the data (to map it to the globe) is one of the causes for miss-located items on the maps.

[cmaxwell]

Actually, this error is caused by the Landsat imagery. Unfortunately, the JPL Landsat imagery is very poorly aligned and stitched together, causing severe problems with geo-accuracy of the imagery in places south of the equator. If you look at a more overall picture of the australia and new zealand area, you'll notice the Landsat "swaths" do not match up well and are off by tens of kilometers in some cases. Lucian is aware of this and he'll be re-making the JPL Landsat mosaic in the future.

In the meantime, we're searching for other sources of data that will hopefully solve this problem of geo-accuracy in Landsat imagery.

Stay tuned.

[ear1grey]

Originally posted by cmaxwell@Nov 9 2004, 05:46 AM
Lucian is aware of this and he'll be re-making the JPL Landsat mosaic in the future.

Quoted post

Hopefully such a resample might resolve the ghosting in southern New Zealand too.

/me attaches example, crosses fingers.

A funny one to demonstrate this problem is if you have a look at Uluru (Ayers Rock) in Australia. You can see the image of it flat on the ground, and then a few kilometres from the image, the land rises up in the shape of the rock. So the rock is there, but its image is a few kilometres off.

[Lucian]

Originally posted by Jonatan Kelu@Nov 19 2004, 12:07 PM
A funny one to demonstrate this problem is if you have a look at Uluru (Ayers Rock) in Australia. You can see the image of it flat on the ground, and then a few kilometres from the image, the land rises up in the shape of the rock. So the rock is there, but its image is a few kilometres off.

Quoted post

That is one bad thing, isn't it. Turns out the precision in the UTM2Geographic transformation I was
using was not that great, I will redo that code for the next version of the mosaic. To make it worse,
about 50% of the scenes were re-processed since I built the mosaic, I assume some georeferencing
errors were caught. It will not be perfect however.
Both the Landsat and the SRTM are georeferenced based on tie-points, which are not very dense
(or well located) in remote areas such as the Australian outback, or most of the south South America.
The SRTM itself is patched in places, so if an area looks funny, it is because data is not available and
has been filled in. The Gibraltar Rock is a good example of that, there are some strange spikes in the
water right next to it!


Lucian

[Lucian]

Oh yeah, the US is aligned right in most places, because it uses the National Elevation Dataset (NED),
not SRTM, and tie-points are very precise and dense.

Lucian

[Bill S]

Originally posted by TomServo@Nov 4 2004, 12:33 PM
Chris mentioned a few times he thinks that applying a curve to the data (to map it to the globe) is one of the causes for miss-located items on the maps.

Quoted post

There also seems to be an issue with altitude - placenames are placed at sea level so their position depends upon which side of the screen they are on: select any area in the Andes, zoom down, then move it across the screen - towns will move from one side of a lake to the other.
Just read of the new enhancements - placenames heightmapped - please ignore this post

Having great fun with this software!