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1: Select a line by pointing at the desired line until it is highlighted
in black. Or select a polygon by placing the tip of the pointer
within the desired polygon. Or do both simultaneously. (Note
that highlighting the edge of a polygon doesn't select the polygon unless
the tip of the pointer is actually inside.)
Step 2: With the right pointer button choose What's This.
Momentarily, the What's This pop-up will appear, providing a Line Description and a Polygon Description.
The Line Description box shows the following fields:
|Entity||Numeric entity label for the line followed by a brief description of that label (usually the first sentence of the definition from the Master Data Dictionary)|
|Theme||Theme with which the line is associated|
|Length||Length of line in your chosen units|
|Vertical Relation||Indicates if line is an underpass or overpass. (Field isn't otherwise shown.)|
|Route(s)||Identification of numbered highways (for Roads & Trails theme only)|
The Polygon Description box shows the following fields:
|Entity||Numeric entity label for the polygon followed by a brief description of that label (usually the first sentence of the definition from the Master Data Dictionary)|
|Theme||Theme with which the polygon is associated|
|Area||Area of polygon in your chosen units|
|Agency(s)||Federal agency which administers the land (for Boundaries theme only)|
Below the description boxes are a couple of preferences buttons.
Clicking the Show IDs button will bring up additional fields. Generally these fields are only of interest to someone who needs to know the nuts and bolts of where the data is coming from.
The Show IDs button is a toggle: if you turn it on, it
will remain on for the remainder of your Place-n-Time session, or until
you turn it off.
Additional fields shown when Show IDs button is on:
|CATD||The pathname of the CATD (catalog) file for the transfer that contains the line or polygon|
|Module||Name of the module within the transfer which contains the line or polygon|
|RCID||The record identity within the module of the line or polygon|
|ATID||The record identity within the primary attribute module which is associated with the line or polygon|
|SNID||The record identity within the node module for the pointnode at the start of the line|
|ENID||The record identity within the node module for the pointnode at the end of the line|
Clicking the Show GNIS button will bring up another field in the polygon description box: GNIS name(s)
The Show GNIS button is a toggle: if you turn it on, it will remain
on for the remainder of your Place-n-Time session, or until you turn
The GNIS database is not part of the SDTS transfer. Therefore there is no direct linkage between the SDTS data and the GNIS data. Consequently, the names provided are really educated guesses at the true name. For this reason the Show GNIS button is off by default. You may choose to turn it on as an aid in identifying polygons, but you should understand that it is only an aid, not an authority.
Within the GNIS name(s) field are the following subfields:
Most probable name(s) - - -
Listed below the Most probable names(s) subfield are the names of nearby entity features, one of which may be the name associated with the selected polygon. To the left of each name is a number which may be used to compare the relative distances from the polygon to the various GNIS names. Although the 'm' following the number does signify meters (independent of your chosen units of measure), you should use these numbers for comparison purposes only: while the value should be fairly accurate for UTM projections, it is a only a very rough approximation for GEO projections.
Other names nearby - - -
To be listed under Most probable name(s), the GNIS name must be located either within the polygon or within a margin of a certain width around the polygon. The actual width varies with the projection and the scale of the source map (i.e., map series). GNIS names listed under Other names nearby are in the area just beyond that margin, but within a distance of four times its width.
There is a special case for reservoirs. If the polygon is identified as a reservoir by the SDTS data, it must also be identified as a reservoir by the GNIS data to be listed under Most probable names; bodies of water which are not considered reservoirs by GNIS will be listed under Other names nearby. You may sometimes find quite a long list of lakes and/or ponds which are "0 m" from the polygon. If you think about it for a moment you will realize that these are places that now live beneath the surface of the reservoir.
Lastly, remember that the area listed is the area of a single polygon,
which is not necessarily the same as the area of the place named in
the GNIS name(s) field. That is because that place may be composed of
multiple polygons on this and possibly other surfaces.
Note that you may copy any or all text from the Line Description and Polygon Description boxes by selecting it with the left pointer button, then moving to your other application and pasting it with the middle pointer button.
Copyright © 2008 by Dapper Mapper
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