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Rasterviewer
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| If you have already read the introduction and want
to go to the Rasterviewer, click HERE!
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| What is the Rasterviewer?
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The Rasterviewer is an addition to the Atlas web site that allows users to see
Digital Raster Graphics (DRGs), satellite imagery, and DOQQ images before they download the data.
In the same fashion that Atlas provides live index maps to help a user find geographic data or maps to download, the Rasterviewer allows Atlas to display the DRG and remotely sensed data.
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| How to Use the Rasterviewer
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The Rasterviewer works similar to the Atlas Downloaders, but there are two major differences.
- First, the database search for the Rasterviewer searches a version of the USGS Geographic Information Names System (GNIS) database and will list any geographic name from GNIS that matches the query. The names in the GNIS database is a compilation of the labels found on all the USGS 7.5' topographic maps.
- Second, the biggest difference from the Downloaders
is evident at the top of the ActiveCGM map. The user
can select vector linework or images or DRGs to be
displayed as a background from map. The user selects
which type of background desired and presses the submit
button to the right of the background choices. Atlas
will redraw the map using the selected background.
If the user selects DRG as a background, then
either the 1:250,000 DRG or 1:24,000 DRGs will display
as a background (depending on current scale of the
map). If the user selects Satellite Image/Aerial
Photographs, then the TM Image of the State or
the available DOQQs will display.
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The user will need to zoom in to change the map scale so that the different backgrounds will activate.
The 7.5' DRGs and the DOQQs become visible when the map width is below 10 km (approximately 6 miles).
The 1:250,000 DRG mosaic becomes visible when the map width is below 250 km.
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| Please keep in mind the following notes:
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- DO
NOT ATTEMPT to view the Rasterviewer
page if you are using a 56K or 28K modem.
Currently, the files being produced by the Rasterviewer
for the Satellite Imagery/Aerial Photographs can be
up to 300Kb in size. Users with these modems will
find these files taking too long to download. There
are plans to introduce compression techniques to decrease
the size of the files.
- Since
the Rasterviewer is relying heavily on Javascripts,
the security setting for your browser may need to
be set to "medium-low".
Use Tools -> Internet Options and then click on
the security tab to set the security for Internet
Explorer.
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| Data Layers Used by the Rasterviewer |
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Major roads from LAGISCD,
Parish outlines from LAGISCD and other sources,
The 1:24,000 Quad Index from LAGISCD,
Place (city and town) polygons,
The Geographic Names Information System from USGS.
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The 1:250,000 DRG mosaic,
The 888 1:24,000 DRGs for the state,
The DOQQs for
the state,
The
1995 TM Satellite Mosaic from the La. Oil Spill
Contingency Plan Map,
The
1990 TM Satellite Mosaic, and
The
2002 TM Panchromatic/RGB 7,5,3 Fusion Satellite
Mosaic
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