Hi all,
Here is a summary of the responses I received to my tiling DRGs question.
Thanks to all those who responded; especially to Mike Jenne who was
particularly helpful in answering my questions.
Phil Uhl
Salt Lake City
> Questions:
>
> Has anyone compiled notes on working with these TIF images? Specifically
> tiling them in a workspace? When you open them in MI aren't they
> automatically placed in the correct geographic position? How do you deal
> with overlap? There really isn't any.
>
> Is the "collar information" the title block, scale, credits and stuff
> around
> the outside of the map in the tif image? Yes
> How do I get rid of it so the maps
> will fit together neatly; or do I even need to worry about it? One report
> from the archives said that if you cut off the outside info in PhotoShop
> you
> also lose the georeferencing.
>
> Does anyone know of a website where you can download quads of Colorado?
>
Responses:
1.The quads I have bought from both SureMap and LandInfo come fully
registered. I stopped using SureMaps and went with LandInfo as they have
been nominated by the USGS in some sort of special distribution realionship.
They can service you with CD(s) in three to six days normally.
LandInfo upon ordeing asks you a couple of questions concerning projection
and the like. I would go for the highest resolution (dpi) in trade for
color info - these maps are only five or six color anyway so four bit color
is OK. The files are in geoTIFF and they gratis a nifty utility known as
WorldReg that converts geoTIFF to TAB. Edge mapping in my experiece of now
four different sets of four to get the those "golden centers" suggests their
registrations are pretty spot on. Line match on teh edges is naother thing
and the quality varies. I have used other tools to build a single image of
the central 4-corners region so that four images didn't have to be loaded.
This requires re-registration and locks you to NAD27, UTM, or State Plane.
MapInfo by design uses the most visible of the images to dominate the afine
presentation. There is a company in Boulder that Bill Thoen can put you
intouch with that can give you a very nice shaded relief of the same maps.
You'll need to invest in the DEM files as well. Ask LandInfo about this and
I am prettry they will direct you in the proper direction. Otherwise drop a
note to Bill
2.if you have not actually purchased your DRGs, you might want to look
at my web site (URL below). We trade standard USGS DRGs (on for one)
across the entire United States. There are coverage maps on the web site;
we have excellent coverage throughout the US. If you don't have DRGs to
trade, we also sell them at reasonable rates ($30, with discounts available
for multiple purchases).
Digital Raster Graphic (DRG) Topographic Map Exchange
www.pipeline.com/~jcsi-maps/drgs
>
3.You can buy trimmed and geo-referenced DRG's from a couple of people.
LandInfo... (800) 390 6277 x 201
One should be able to tile these perfectly.
Their price is about $99 per quad sheet, typically $2-3k per state.
4.What you need is a commercial product that is already available.
Seamless quads, already linked and ready for use in Mapinfo. Called
Sure Map Raster by Horizon Technologies. We are a dealer in So.
Calif. if you want to see some, or check out horizons.com the mfg.
5.A relatively new offering is the "Quad Companion" (~$300) which has the
ability to seam multiple 7.5' DRG's into a single geo-referenced image and
clip the collar information. For a commercial product Land Info offers
nation
wide coverage, cropped and seamless, 250 or 400 dpi for all scales from
1:24,000 to 1:500K. Reasonably priced and high quality. As for cheap
availability of DRG's there are a number of DRG exchange groups in
existence.
Additional note: DRGs appear to be automatically oriented to grid north in
MapInfo.
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