SO432, GIS Fall 2008

NGA  Data Exercise

Update the help file and the MICRODEM excecutable (do this before getting the data sets).

Download the new data set, NGA raster data.

Download the new data set, Norfolk VPF  raster data.

Vector data

Using the VPF button on the main toolbar in MICRODEM, open the file C:\mapdata\indexed_data\vpf-shapes\VM2ALV2\NORFOLK\vpf_index.vpf.

What does the first map displayed show?  Why does the program do this, and not display the entire data set? 

Display the map at "This map, full detail".  Is this map useful?  What does it say about the proper "scale" for this data set?  Get a screen display showing the scale at which this map should be displayed.

This data base consists of 10.5 MB of vector data (which compresses to 1.6 MB).  This is a small sample data set; a full data set would be 10s of times larger (in the 100's of MB), with the same level of detail but covering a larger area.  What would you predict about how you could display such a larger data set?

Can you turn off layers on the map? (Right click, Modify VPF layers displayed)

If you do an ID operation on a symbol on the map, what kinds of information is displayed about the records in the data base?  Are the codings human readable?   If you look at the two files "ATT_DECS.DBF" and "ATT_VAL.DBF", both in the same directory as the MICRODEM program, do they help interpreting the coding?

Open the file  C:\mapdata\indexed_data\vpf-shapes\VM2ALV2\NORFOLK\vpf_index.vpf  as a database in MICRODEM.  What is in this file?  Where is the actual map data for the VMAP?

There are files in the data set with the extensions PFT, LFT, and AFT?  Is there any meaning to these extensions?

Find the data file(s) for the roads.  What format are they in?  How does the computer know how to draw the roads, and how many different categories are on the map?

Raster Data

Open the RPF files in c:\mapdata\nga_raster_data:  Can you estimate the date of the CIB imagery?

• Hood1MCIB (and then get the metadata, with "File, Image metadata")
• Hood5MCIB (and then get the metadata, with "File, Image metadata")
• Irwin5MCIB (and then get the metadata, with "File, Image metadata")
• Irwin10MCIB (and then get the metadata, with "File, Image metadata")

Open the CADRG:

• IriwinONC
• IrwinJNC
• IrwinTPC
• IrwinMIM
• IrwinGNC
• IrwinTLM50
• IrwinJOG

There is an airfield about N35.28, W116.63.  How long is the main runway on, and do you trust this number?

• The JOG
• The TLM50
• The 10 m CIB

The Indian Springs AF Aux field is at N36.75, W115.71.  How long is the main runway on, and do you trust this number?:

• The GNC

You can compute the magnetic variation using the Cartography, Magnetic Variation Values.  How much does this vary:

• Over the TLM tile?  Would ground forces need to worry about this variation, and would they need to use different values over the map?
• Over the JOG tile?
• Over the GNC?  Would air forces need to worry about this variation, and would they need to use different values over the map?

There is a line labeled "14˚" running diagonally across several of the CADRG tiles.  What do you think it represents?

• JOGA
• ONC
• GNC (on this one it is "16˚" in the upper left corner)

Note that the TLM50 has a UTM/MGRS grid.  Put a MICRODEM grid on the map, and use two different datums.  Which is on the map, and why do you think NGA did this?