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Navigation Instructions
This section provides basic
instructions for navigating the HEPGIS web applications.
Application Tabs -
Select a tab to switch between the different applications.
Map
Extent and Info Tool Bar - 
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Initial
Map - Select the tool to return to the original map extent (the
Conterminous United States).
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Zoom
Out - Select the tool then click on the map to display a
larger portion of the map.
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Zoom
In - Select the tool then click on the map, or drag the Cursor
across the map to form a box around the desired map area to be viewed.
The map will zoom in and display the selected map area.
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Pan - Select the tool then click on the map or drag
the cursor on the map to recenter the map.
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Info - Select the tool then click on a location on the
map to identify the features for that location. A Data Layer List Table
will appear below the map window listing the name of the layers and the name of
the selected feature for each layer. Click on a data layer
feature name in the Table, such as 'Cook IL' for the 'County' layer.
The data for that county will then be listed in Data Grid
below the Data Layer List Table.
Info
Tool - Data Layer List Table
Info Tool - Data Grid
Map Selector
- Click on down arrow button to get a drop-down menu listing
the available maps. Select a map name and the selected map will be drawn
in the Map Window.
Change
Location Button - Select the Change Location Button. In
the table that opens below the button, type the desired location. To
locate a street address type the Street, City and
State. To locate a city type the City and
State. To locate a state type the State.
To locate a zip code area type the Zip
Code. To locate an airport type the Airport
Code. Click Find. The location specified will then
be displayed in the Map Window.
Change
Layer Button - Select the Change Layer Button. In the
table that opens below the button, check the layers to be displayed on the
map. Click Redraw, to redraw the map and display the layers.
Some layers will only be visible at certain map scales, for instance the
smallest map scale that Railroads will be visible is 1:250,000.
Query
Tool Button -
Select the 'Select By Query' Tool Button. The Query Tool will open below
the map window.
A
query allows the user to identify geographic features based on certain
criteria. An example of a Query is - 'Find the Counties in
Massachusetts with a population greater than 100,000'.
Build a query string with this criteria and submit it to the application. The
result is a list of selected items that appear in a table below the map window.
Building a Query String:
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Click on the down arrow of the 'Select Layer' dropdown box to
get a list of layers. Select a layer from the list.
This will fill the 'Select Field' dropdown box with the fields that are related
to the selected layer.
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Click on the down arrow of the 'Select Field' dropdown box to
get a list of fields .Select a field from the list.
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Click on the down arrow of the 'Operator'
dropdown box and select an operator.
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Enter a value in the Text Box next to the 'Operator' dropdown
box.
An example of an appropriate value for the selected field will appear next to
the text box when you select a field to query.
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Click on the 'Add to Query' button to add the values (Field,
Operator, and Text Box) to the Query String Box that is to the
right of the 'Add to Query' button.
An example of a correct query string is:
Population > 10000000. ('Field' 'Operator' 'Value')
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If you would like to add to the query string, add an operator such as 'And' by
clicking the 'And' button.
Other operators are 'Or', 'Not', and you can add parentheses.
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Then add another query string by following steps 2 - 5.
An example of a final Query String for layer 'County':
Population > 100000 AND State = "MA".
Note:
Only one layer can be queried in one final query string.
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To undo the last entry added to the query string click the 'Undo'
button.
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To clear the entire query string to start over click the 'Clear'
button.
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When the query string is complete, click on the 'Submit Query'
button and the query will be processed.
A table will appear below the map window with the results of your query.
If you would like to 'zoom' to a particular selected item, click on the
'Zoom to Item' text in the left column of the table.
The map will zoom in and display that item.
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Note:
There is a selection limit of 500 records.
For some queries it is advised to first choose a State and then add to
that query string. An example
query would be: State = "CT" AND Facility Type = "Amtrak Station"
Printable Map Button -
Select the Printable Map Button. A new browser will open with the map,
legend and title displayed. The print menu will automatically
open. The user can then print the map layout displayed in the
browser window.
Save Map Image Button - Select the Save
Map Image Button. A new browser will open with the map displayed.
The user can now save this map image to a file by clicking on the File Menu in
the Browser and Save As. You should have a choice of saving the image to
a PNG or Bitmap.
Save Legend Image Button -
Select the Save Legend Image Button. A new Browser will open with the
legend displayed. The user can now save this legend to a file by clicking
on the File Menu in the Browser and Save As. You should have a choice of
saving the image to a PNG or Bitmap.
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