Exporting Base Maps to Petra from All Topo Maps

Importing Maps into Petra

Petra is a product of “geoPLUS Corporation” (918) 971-7071, www.geoplus.com.

Petra provides unique, PC-based solutions to data management, manipulation, visualization, interpretation, and integration of geological, geophysical, petrophysical and engineering data. Results can be quickly visualized using the interactive cross-sections, mapping, log plots, cross-plots, custom spreadsheets, horizon and fault picking, trace processing and mathematics, and synthetics.

You can easily build full coverage maps for Petra projects with BigTopo7. Let’s build and register a basemap for the Petra Tutorial Project.

Maps exported from BigTopo are ‘UTM Projection’ so first set the Petra project projection to UTM. Select the main menu option “Project: Settings…: Set Map Projection…”:

On the Petra ‘Map Projection Settings’ dialog choose:

‘UTM (Northern Hemisphere)’

Next check the U.T.M. Zone Number. The Petra Tutorial Project is centered around 29.5 N 95.0 W and the natural UTM Zone is 15. If you don’t know the correct UTM zone for your project, BigTopo will display the correct zone when we make the coverage map and you can return to the ‘Map Projection Settings’ dialog and match the basemap.

Next select the Petra Ellipsoid. If plan on exporting a NAD27 datum map from BigTopo set the Petra Ellipsoid to ‘Clarke 1866’ (NAD83 = ‘GRS80’):

Press the [Save] button, then press the ‘Mapping’ toolbar button to display the Petra mapping module.

Petra will display the extents of the current project. Select the Map menu option ‘Display: Show Map Limits…’:

Petra will display the geographic limits of the current project:

In this case the north west corner is ‘29.597 N 95.038 W’ and the south east corner is ’29.560 N 94.993 W’. Since we know the project extents, we can use BigTopo to build a single base map for the project. Start BigTopo7,

Uncheck the ‘Recolor’ option on BigTopo’s ‘Annotation’ tab, lock the ‘North West Corner Coordinate’ and enter the project extents into the North West and South East coordinate boxes. BigTopo will automatically compute the width and height.

Note that once the North West and South East coordinates are entered, BigTopo displays the UTM Zone number in the center of the green box (in this example it is Zone 15.)

Select the ‘Output File’ tab, select the ‘Export BigTopo as generic graphic picture’ option, choose an appropriate filename and path. Set ‘Compression’ to ‘TIF 8-Bit Packbits compression; $2’. ( Petra can not read LZW compressed TIF images.) BigTopo7 will automatically write a .TFW worldfile which Petra will use to place the base map under the project.

Click on the ‘Build BigTopo’ tab and press the ‘Make BigTopo’ button to build the basemap. Close BigTopo.

In the Petra Map tool, press the toolbar button ‘Add Image’:

Then use the mouse cursor to draw a box anywhere on the drawing. The box position and size are not important.

Petra will display the ‘Overlay Image Attributes’ dialog.

Press the ‘Browse’ button to prompt with the ‘Select Image File’ dialog, browse for the basemap file and press [Open]:

Select the ‘Options’ tab (on the ‘Overlay Image Attributes’ dialog), then press the [Select File] button and browse for the .TFW worldfile:

Press [OK] and Petra will load the basemap, place it in the correct place under your vector annotations.