| Downloading And Loading Base Maps Into ArcView | |
| Base maps are maps which underlie other layers of visual information (i.e., archaeological site shapes you are creating). Base maps used in ArcView usually consist of USGS Topographic digital raster graphics (DRG), digital orthophoto quarter quadrangles (DOQ), or county transportation maps. | |
| Obtaining Quad Maps | Iowa Department of Natural Resources NRGIS Library (Natural Resources Geographic Information System) has USGS 7.5' Topographic Maps in a downloadable format along with the "world files" for each map which are necessary to place the map picture into the right georeferenced area within ArcView. They also have instructions on how to unzip and save these files for use in ArcView on the downloading pages and also in a help page. |
| Bring Into ArcView | Load map as an Image Theme: 1. click the Add Theme  button; 2. switch the Data Source Type to 'Image Data Source'; 3. navigate to the drive your map file is stored in, then to the directory; 4. select the map, and hit OK. The map will momentarily be loaded into the top of the Table of Contents of your active View. 5. The layers of visual materials to be displayed in the View are 'stacked' in the Table of Contents. Themes at the Table-of-Contents bottom will underlay the higher-up themes as a pizza crust underlays its toppings: sometimes, you can see parts of the crust through the toppings; but if you put the crust above, you can't see the toppings at all. The particular visual effect depends on the layering, what is 'checkmarked on,' what is 'uncheckmarked/off,' if any queries/selections have been made, and if a theme is in edit mode. Right now, you want your shapefile ('Feature') themes to be placed higher in the View's Table of Contents so that they overlay the map ('Image') theme. To do this, click-hold-and-drag-and-drop the Theme's name within the View's Table of Contents to position the quad map ('Image') theme (i.e., Drgp42c.tif) lower than your shapefile (you may do this later if the shapefile doesn't exist in the View yet). 6. Then 'checkmark on' the themes you want to display (i.e., the drg map, the shapefile); doing so in bottom-to-top order will display the graphics faster.  7. In order to retain these project additions for your next session, go "File" menu "Save Project As...", and hit "OK". 8. Problems loading maps? First, try the "Zoom to Active Theme(s)" button  . Then, if you still have trouble loading DOQ maps with the .jpg file extension, make sure the "JPEG (JFIF) Image Support" ArcView extension is turned on in this ArcView project. Similarly, if loading DRG maps with the .tif file extension presents difficulties, try adding the "TIFF 6.0 Image Support" ArcView extension (see "ArcView Projects" Step 5 for details). |