GMAP4

[bobmaloney@compuserve.com]

Today, on FreeGeographyTools.com, I found a reference to GMAP4 (www.mappingsupport.com/p/gmap4.html).

GMAP4 adds to Google maps by allowing downloads of USGS TOPO MAPS and Canadian TOPO maps from mytopo.com. The TOPO maps are superior to the TERRASERVER maps. I believe the TOPO maps are the  the TOPO maps that MAPTECH used to sell with MAPTECH NAVIGATOR.

 MYTOPO purchased the MAPTECH system from MAPTECH in the last year or so.

Apparently, MYTOPO is giving the maps away free, at least to GMAP4!

The maps ARE better than those on TERRASERVE. I recommend that TOPOFUSION look at the what MYTOPO is giving away and see if it can be included in the TOPOFUSION system.

                                          Bob M

[ScottMorris]

Interesting, thanks for the note.  I have seen MyTopo maps as a part of other google maps based sites, but hadn't really looked at the details yet.

I did a quick scan and while the topos look good in some places, some are faint and I've noticed some registration problems:



Still, I would love to add this as an alternate to Terraserver.

However, the functionality of TF may be such that they aren't keen on us using their maps.  The fact that TF stores/caches map data permanent, that it includes a batch download tool and some other considerations might make it hard.

But I will try contacting them and see what they think.

[bobmaloney@compuserve.com]

After looking at a lot of MYTOPO images and TERRASERV  images with TOPOFUSION shading. I have come to the conclusion that the MYTOPO images are not that much better than the shading enhanced TERRASERV images available through TOPOFUSION.

Still, it would be nice to have the MYTOPO images available under TOPOFUSION.

If storing the MYTOPO images is a problem with them. I would have no problem in just getting them on the fly. Incidentally OZIEXPLORER now lets us load GOOGLE EARTH images but stops you from loading them. This works fine.

Keep up the good work,

                         Bob M

 



 

[Joseph Elfelt]

Bob,

Thanks for noticing Gmap4.  I am the author.  Here is a link to Gmap4 showing the MyTopo maps for the area in the image posted by Scott.
http://www.mappingsupport.com/p/gmap4.php?ll=32.374489,-110.772572

And here is a Terraserver link for the same area:
http://terraserver-usa.com/image.aspx?T=2&S=12&X=651&Y=4476&Z=12&W=3

Note that these two links appear to show different generations of USGS maps.  For example, the MyTopo version has section lines while the Terraserver version does not.  My understanding is that Terraserver has never been updated with newer USGS maps.  By contrast, the MyTopo company continues to scan all USGS maps as they are released and always has the latest version loaded on their tile server. 

Now focus on the lower half of this map area and compare the MyTopo and Terraserver maps.  To my eye at least, the MyTopo map has significantly better resolution.  Perhaps that reflects improvements in scanning technology - but that's just a guess.

Yes, I've also seen some alignment issues with MyTopo maps (and also with Terraserver).  Recently I traded email with the MyTopo staff and asked about this.  They said alignment issues have two causes:
1.  Mistakes in tile seaming
2.  Adjoining maps that the USGS produced with different datums.

#1 they can fix and are anxious to do so.
#2 cannot be fixed without warping the map to distort it and as a policy matter they have chosen not to do that.

The MyTopo people invite everyone to report mis-alignments so they can determine  whether they are fixable.  They can be reached at  support@mytopo.com

Regards,
Joseph

[ScottMorris]

Thanks for the post Joseph.  You are right that in general the myTopo maps seem to be of higher quality, in terms of scan and dates.  I certainly meant them no slight.

It was just a little strange to find a bad registration error within the first minute of panning around close to home.  You are correct that Terraserver has its issues with this too, particularly in California. 

I will be checking out GMAP4 in more detail -- I work on another project, http://trackleaders.com, that could greatly benefit from your API.  It looks very well done.

Thanks.

[Joseph Elfelt]

Scott,

Yeah, I'm kinda surprised too at how easy it is to find seams that are 'off'.  Most of the time when I have seen that and then look close it becomes apparent that the adjoining maps are from different generations of maps.  Perhaps that's when the USGS shifted from NAD27 to NAD83.

On the other hand - the price is right.

Just wanted to clarify one thing.  The API is not "mine".  The MyTopo folks developed the API and I am just a lowly user of that API. 

Thanks for indicating you will check in with the MyTopo folks regarding your ideas for possibly using their API.  We certainly don't want to kill this goose.

And I looked at the Tracker site - what a neat idea.  Adding MyTopo maps to that site would be really cool.