Hi PriceCollins.

This Unusual Flare or Diamond appears to be pink.
It is pointing South West,North West and North East.

All the best,

ploppy

Yes I Understand, by why even the image of DG 2002 , 2003, and 2008 are exactly with the same clouds, and for all that part of Africa, even in World Wind I have the same thing ( I knows you take the images at the same " warehoouse" but with the same clouds for different years ???.

thanks
Michel, Qu�bec , Canada.

I observe systematic errors of longitude differing by about 2 seconds (corresponding to about 200 feet) from positions measured on USGS topo maps in California, New Mexico and Puerto Rico. These errors are always in the same direction, pertain only to the longitude, and so cannot reasonably be attributed to "inaccuracy" which would exhibit randomness in both size and direction.

The GE west longitude is always a larger number than the USGS west longitude describing the same feature on the surface of the earth.

Does anyone know if these differences arise from referencing a different zero longitude, or for some other reason, or what ?

Please provide examples.

For example:

The famous monument XXX is noted in the book "FFF FFF" (or on Map "GG GGG" at Web URL http:///www.topozone.com/...) to be located at
YY.YYYYYY N ZZZ.ZZZZZZ W in San Diego, California. However, the Google Earth images show it 200 feet west of that point

My examples aren't famous monuments, just points that I have had occasion to work with for my own purposes. One of them is the NE corner of Section 33, Township 15N, Range 8E in Santa Fe County, as shown on the USGS 7.5 minute quadrangle "Picture Rock"

That point measures as 35 deg 29 min 26.2 sec N and 106 deg 5 min 21.3 sec West on the USGS quadrangle "Picture Rock".

When I hover the Google Earth cursor on the same point, I read 106 deg 5 min 23.3 West in the caption on the bottom of the GE view. I won't quibble about one or two tenths of a second since the cursor itself is bigger than that, but 2 seconds is unmistakable.

I found similar discrepancies with a USGS topo map in California and a USGS topo map in Puerto Rico, but didn't note down the exact points at the time.

If you have a USGS topo map handy, I would suggest picking any point you can conveniently identify and carefully measure its position, taking care to apply correct scale factors to your ruler, then find the same point on GE and see for yourself. The measuring is simpler (or a non-issue) if you pick a point that is near (or already precisely on) a latitude/longitude mark on the map, but that may not happen to be something distinctive that is visually obvious on GE. If not, then you may need to go through the tedium of measuring somewhere not near a lat/long marker.

I am surprised if this is the first time this issue has arisen? When GE first came on the scene there must have been dozens if not hundreds of amateurs and professionals who would have made it a point to check out the accuracy compared to already established maps, and USGS topos would have been the most widely available for comparison. Is this really the first time the question has come up ?

Picture Rock, New Mexico is shown on the USGS topographic map at Trails.com as being at
35.491702,-106.079466
= 35�29'30.13" N 106� 4' 46.08" W
which is not the location you indicate.

You can confirm the correctness of the Google Earth and Google Maps imagery at that location on
MountainZone.com Web page

Sorry to be slow to reply.
I did not say I was measuring the object "Picture Rock", I was only speaking of a particular point on the quadrangle MAP, the quadrangle map's name is Picture Rock. It doesn't matter, you can pick any point you like on that (or any?) paper quadrangle and compare its longitude on the paper map with the longitude of the same point on GE.
Anyway, I think I have a PARTIAL answer to my question, because I see the the paper map says "North American Datum 1927", but on trails.com, there is notation "NAD83/WGS84", which I suppose means North American Datum 1983. That particular map on trails.com agrees with GE, but they are both different than the USGS quadrangle on paper.
What I don't know is what is the definition of "North American Datum" and why it should ever change. Since the choice of zero longitude is completely arbitrary and was chosen in or near Greenwich, England many years ago, why would it ever change, except possibly for political reasons ? Changing something so fundamental wreaks havoc throughout communities who have established long traditions, work and documents (maps) based on the original standard.
We aren't talking about continental drift here which is only a few inches per year, the observed discrepancies are on the order of hundreds of feet.
Regards,
Bill Dempster

See this thread.

Here's a few tickmarks, plus a part of a photo ID, from some images by the Province of British Columbia. I looked a bit for some others but couldn't find any.

There's also a ton of pieces of lint all through their imagery but far too numerous to mention.

Thanks, Hill, for giving the other thread. The comment in that thread that is most pertinent is that of unruh on 3/16/08 which points out that the assignment of 0 longitude is completely arbitrary. That anyone would ever tamper with the definition of 0 longitude once established is an abomination. But, I still don't know why there would still be further changes as between North American Datum 1927 and something more recent (like WGS84?) unless it was discovered that there were inconsistencies in the 1927 reference and it became necessary to make changes to reconcile worldwide mapping. ??