UAF Geology and Geophysics-Plotting Points on USGS Maps in MapInfo GIS

Background

The basic assumption here is that you have a bunch (more than you want to do by hand) of points that you want to plot on a USGS topographic sheet (1:250,000, 1:63,360, or 1:25,000). Of course, if your points cover a very small (say, less than ~200 m) or very large (greater than ~200km) scale area, then it doesn’t really make sense to plot on a USGS topo sheet.

You must also have the locations of the points specified by Lat/Lon or UTM coordinates to a level of accuracy suitable to the map scale you are plotting. No need to be more accurate than 2 meters, but you should be at least as accurate as +/- 100 meters. Here we assume you have this data as an MS Excel file with location info as two separate columns

Here we assume we will plot everything on one USGS sheet, stitching topo sheets together is possible but not covered here.

Download Map

The USGS makes data for Alaska available at several websites. The exact content and location of these sites is continually changing. In January 2001, the site at http://agdc.usgs.gov/data/usgs/geodata/ was quite good. These are bitmaps (as .tif files) of the printed USGS sheets. Even though they do not (generally) download with a .zip extension, they ARE compressed and have to be uncompressed (use the winzip utility).

When you download the maps, make sure you download the associated .tfw file (an Arcview world file). These two files (as an example, the Circle Quad would be c65144a1.tif and c65144a1.tfw) together register the pixels of the bitmap into UTM coordinates. That’s right – the Northing and Easting (in meters) of each pixel is specified – how cool is that!? When you download the .tfw file your browser will probably just open the text file and display it. No problem, just copy the text and paste into a text file (use the notepad accessory, check in NT explorer to make sure the extension is .tfw). Your .tif and .tfw files should have the same names but different extensions (eg., c65144a1.tif and c65144a1.tfw).

Groom Data

If you have Lat/Lon in degrees, minutes, seconds (or degrees and decimal minutes), or Lat/Lon in the same column, you should convert them to decimal degrees Latitude and Longitude (west as negative values of longitude) in Excel. You can include other data in this spreadsheet – it will be imported into the MapInfo table along with the location info and be available for other analysis (contouring, labels, etc.). At the minimum you’ll probably want a Station ID, Lat. And Lon.

Bring A Registered USGS Map into MapInfo

Launch the MapInfo application. From the menubar select WorldReg … World Registration. This is a third party add-in to MapInfo which has to be downloaded and added to the application, at UAF Geology & Geophysics this software is already added in – at other installations you will have to download and add install it. A dialog box will ask you to specify the bitmap (raster) file type – for USGS maps this type is .tif, but if you have other data types (satellite images, airphotos, etc. you will have to specify the type).

At this point a standard open file dialog will appear, browse to your .tif file and select it – if you haven’t messed up the file names, the application will automatically find the .tfw file. If you haven’t decompressed the bitmap you will get an error here. Check that the World File Details are correct – the pixels sizes, corner of the map, scale, datum, and UTM zone should make sense.

MapInfo will ask for a Table Name. The fundamental container for data in MapInfo is a Table – anything you import will have a table name – when you import a map, go with the default (c65144.tab for the circle quad).

At this time, MapInfo will open a Map window for the c65144.tab table and you can use the tools in the Main toolbar to zoom in/out and scroll through the map.

Bring Data Into MapInfo

A cool feature of MapInfo is that one can parse MS Excel files directly into MapInfo. That might seem like a mindless feature, but remember than MapInfo works on DATABASE tables and MS Excel data is a SPREADSHEET. In Arcview (for example) you must first convert your MS Excel sheet to a database and then import it (either way you are doing the SAME thing).

In MapInfo, select File … Open Table. MapInfo originally looks to open MapInfo tables (*.tab). Change the file type selection in the dialog box, under “Files of Type:” to Microsoft Excel. Browse to the locaition of your Excel file and click open.

At this point you can save yourself a LOT of work by looking at your Excel spreadsheet and locating where the data begins. For example, if you have column labels in Row 1, start the import in Row 2 and specify that the line above the data is column titles. For the Steese data, the Named Range will be: Steese99!A2:AJ1558 (Note that MapInfo uses the MS Excel protocols to separate the sheetname from the cell range with a ! character and the : character to separate the upper left cell from the lower right).

This will open up a browser window, in which you should find the MS Excel data. Because the data came from a spreadsheet we have to specify data types for the columns (the table structure) in order to complete the conversion to a database.

MapInfo opens tables as read-only so we cannot change the table structure immediately. First save a copy of the imported table with a new name (eg., Steese2), close the original table, and open the new table.

Use the command: File … Save copy as:, then select the name of the table (you should only have two open tables – the map[c65144, in the steese example] and the imported table[steese, in the steese example]), select the imported table [steese, in the steese example], and pick a NEW name [steese2, in the steese example]. Steese2 will not be read-only and we can modify the table structure as we wish.

Close the read-only version. Select File … Close table, and pick the current table to close. Now select File … Open table, and select the table to open [Steese2 in the Steese example].

With the new table browser open, select Table … Maintenance … Table Structure. This will open a dialog box in which you can modify the structure of the table. You can do a LOT here, this is where you modify the database structures to fit the data and the problem you are solving. In this cookbook, we will only check/change two important things.

First, make sure the latitude and longitude columns are of the type “float” (floating point data are numbers where the decimal point is not locked into – they float -- a given position). You should not have to change this for the Steese data set.

Second, you must associate the table with a map projection and datum. To do this click the check box “Table is mappable”, and the click the projection button which appears. At this point we are assuming that the Lon/Lat data in the MS Excel table is in the same datum as the USGS maps (NAD 27). At some scales, this might not be an issue (we’re talking about horizontal errors of +/- 500 meters), but it is important to know what datum your locations was collected in. If you collected the locations in NAD 83 and want to convert, we have programs in the lab that do that.

Assuming the data is NAD27, under categories: select Longitude/Latitude, and under category members: select Longitude and Latitude (NAD 27 for Alaska).

After you have select a projection, click OK on the Modify Table Structure dialog box.

Although the table has Longitudes and latitudes in it we have to identify those columns, select a symbol before we can plot the points. Select Table … Create Points, and identify the X coordinate as Longitude, and the Y coordinate as Latitude. There is no need to modify the projection in this dialog box.

Although the table now includes the definition of the points we need to bring that table into the USGS map window.

Select the c65144a map window, select Map … Layer Control and click the Add button. This layer control dialog is very similar to the layer control in Corel Draw or Adobe Illustrator. If the table you added is above the map it will plot on top of the base map. Make sure the table is visible and appears above the base map and click OK.

You should see a swarm of points on the Circle Quad with the example data.

Using Geologic Symbols in Your Maps

The same symbol set (GeoSymbol from Pangaea Scientific) which is available in CorelDraw is also available in MapInfo. To select the GeoSymbol font:

With MapInfo running
Select Options ... Symbol Style
In the Symbol Style dialog box select the Geology font
Pick the symbol you wish from the pull down menu.
The previews are fairly ugly, you can use the GeoSymbol card in the lab to find your favorite symbol.
The rotation convention is counterclockwise, but is useful for placing s/d symbols.

Compose a Layout to Print on Large Format Printer

Here we assume you have already added the DesignJet Printer and we are printing the Steese data set. The specifics here depend, of course, on your data.

Whatever appears in you map window will print on the page. A good way to fit the data to the window is to right click on the map window and select “View Entire Layer” and select Steese2.

The definition of which map windows print where on the page in MapInfo is controlled in Layout windows. To create a layout select Window … New Layout Window. Select the top option “one layout for the current Map window”, click OK.

Now specify the printer and papersize. Select File … Page Setup. Click the Printer button, select the DesignJet 750C printer. Click the Properties button and select landscape button. Click the More Sizes button and select a paper size 36” wide by 20” high.

The Layout window should show a blank piece of paper 36” wide by 20” high. If it appears some of the paper is missing, then right click on the layout and select View Entire Layout.

In a Layout Window, Map Windows are displayed in Frames. So now specify a frame in the layout. Use the Frame tool from the Drawing Toolbar. (If you’ve lost the Drawing Toolbar, you can bring them back by right clicking up among the toolbars to get the Toolbar Options dialog.)

With the Frame Tool, click-drag an insertion box onto the printable (white) portion of the layout. When you release the mouse a Frame Object dialog appears and allows you to confirm the scale – if you don’t mind an odd scale (1” = 1.330 miles, for example), click OK – otherwise you can select an even scale (1” = 1.5 miles).

IF you want an exact scale on your paper, the way to go is to:

Determine the Frame width in the layout in cms.
Determine the appropriate final (on paper) scale.
Use the following formulae:
((Frame Width in Inches * Scale) /12) /5280 = Map Zoom (miles), or
((Frame Width in cms. * Scale) /100,000 = Map Zoom (kms).
Then, in the Map Browser set the Map Zoom (Map ... Change View).

Embellishments

This cookbook will get you going, but look into the MapInfo’s help screens for adding scale bars and north arrows (see the cosmetic layer), adding contoured overlays (see Vertical Mapper), or generating graphics and perspective views.

revised November 2001