Overview of ArcMap
Below is the main view window in ArcMap. I will try to point out the main features.
Adding and editing geographic features and attributes in ArcMap
Now you have the image index shapefile loaded in the map view for Chemung County . It should be already visible, if not click in the checkbox to the left of the index layer and it will be drawn. Zoom to the Chemung County image index file by right-clicking on the index layer in the legend (layer) window, and then clicking Z oom To Layer from the dropdown menu. Notice some of the other choices in the dropdown menu.
Now that your map window is zoomed to Chemung County , you can change the display properties of the index layer so that you can see where you are.
Double-click on the layer symbol under the layer name in the layer window.
Change the Category to Hollow, the Outline Width to 2, and the Outline Color to Blue.
Click OK and see how this changes the layer in the map view. You can use this same process to display any shapefile that you have loaded in the map view. Remember that they act as layers where they are stacked on top of each other. So the ones below can only be seen if the one on top is transparent.
Use the Select Features button to select the polygons from the image index layer where the farm is located. Once selected, the polygons will change color. Then click the Add DOQ button to load the images.
When you click the Add DOQ button a window will open to ask you for the field in the index shapefile table where the image names are located. Click the radio button next to ‘FILENAME' and the click Insert Raster . This may take a few seconds depending on how fast your computer is and how many images you chose to load.
Once the images are loaded, you can use the Zoom In button to zoom to the farm or to the field that you will start digitizing.
You can now add the new (empty) shapefile created in ArcCatalog to ArcMap to begin the actual field digitizing process. Nothing will show on the map because here are no features in the shape file yet.
Click the Add Data button from the toolbar and navigate to the folder where the new shapefile was stored. Then highlight that shapefile and click OK to add it to the map view.
Change the symbol for the new shapefile to transparent and select an outline color that will show up well against the aerial imagery. Now you can begin digitizing the field boundary polygons.
Once you have added the new shapefile, make the Editor toolbar visible if it is not already. Click View-Toolbars-Editor .
When you click Start Editing , choose the new shapefile from the window that is opened and click OK.
Look at the Editor toolbar to make sure that the Task you are performing is the Create New Feature and the correct Target is the new shape file, in this example Stow .
Make sure you are zoomed to the field you want to digitize. If it is small enough, you may be able to see the entire field, if not zoom to where you can clearly see the field boundary. You will be able to pan around the entire field as you digitize.
Click on the Sketch Tool button to begin digitizing. Place the cursor on the map where you want to begin your new polygon feature, you should see a circle with a cross-hair in it, and click once. Then go to the next point that defines your polgyon and click again. Continue doing this until you are almost back to the last point. To close the polygon, double-click on the next-to-last point, or press F2 after the next-to-last point. If you get messed up, you can either double-click to finish, and then press the Delete key on the keyboard to delete what you have drawn and start over, or you can right-click and choose Delete Sketch . It may take a few attempts to get it right. If you click a point that you want to delete, hold the curser over that point and right-click, choose Delete Vertex from the dropdown menu and continue on. See second screenshot below.
If you cannot see the entire field as you are digitizing, you can pan around the image and then resume digitizing as follows. Click the last point in your field and then move your curser out of the map window and choose the Pan button from the toolbar. This will deactivate the Sketch tool while you use the Pan tool to move the image in the map window where you want it. When done moving the image, click the Sketch tool and resume digitizing.
If a group of fields are adjacent, it may be easier to digitize the entire boundary at first and the go back and split the fields up. In the screenshot above, a group of adjacent fields have been digitized and will be split up using a polygon feature editor from the Task dropdown list.
Click on the Task dropdown menu and choose Cut Polygon Features . Then click on the Sketch Tool and start by moving your cursor outside of the polygon to be split, so that you can start digitizing the line where you want to split the polygon. You must start outside of the original polygon and end outside of it as well. Double-click to end your line and the polygon will be split.
If you want to delete or digitize islands within the field polygons, for example ponds or patches of trees, you will need to follow this process.
Use the Select Feature tool to select the field polygon you want to work with. Click on the Task dropdown menu and choose Cut Polygon Features . Then click on the Sketch Tool and start by moving your cursor outside of the polygon to be split, so that you can start digitizing the line where you want to split the polygon. You must start outside of the original polygon and end outside of it as well. Digitize the line from outside the field polygon to the pond and around it and then end outside of the field polygon. See example to the left. Double-click to end your line and the polygon will be split.
Start with a second line to split the remainder of the pond up as seen to the right.
When both parts of the pond have been digitized, use the Select Feature tool to select the main field and the small part that was split out between the pond and the edge of the field. Drag your curser around both parts of the polygons to select them as the active features. Click on the Editor button to see the dropdown menu. Choose Merge from the dropdown menu.
Then the field will be reconnected as one polygon with pond left as a separate polygon inside the field. You can delete the pond if you wish by selecting the pond polygon and hitting the delete key. Or you can keep it as part of the farm field shapefile.
When you are finished digitizing all of the fields for that farm, you can then enter the field id information. This can be done as you digitize but I prefer to wait until all of the fields are done. Right-click on the new field shapefile and choose Zoom To Layer from the dropdown menu. Now you can see all of the fields you have digitized.
Click on the Edit tool , then move your cursor over one of the fields and Right-click, choose Attributes from the dropdown menu. This will open an Attribute Editor window where you can enter the field data on the fly.
Use the Attribute Editor window to enter the field id and field names for all of the fields you have digitized. Once it is opened you only need to click on the fields and they will become active for editing
When finished click on the Editor button and choose Stop Editing from the dropdown menu. Be sure to save your edits when prompted or the field boundaries and all of the information you entered will be lost and you will have to redo all that you had done.
The last step is to calculate the acreage of the fields. Make sure that the new field shapefile is highlighted in the layer window. Click on the Calculate Area/Acres button from the toolbar. If you get this error window, then you forgot to set the spatial reference information (coordinate system) in ArcCatalog.
Now Right-click on the new field shapefile in the Layer window and choose Open Attribute Table. This will open the attribute table so you can see the data that was entered and the area calculation.
If you want to use the attribute data in Excel you can export the table as a DBF file that can be opened in Excel.
Click the Options button in the table window and choose Export from the dropdown menu. Make sure you export All Records if that is what you want and choose a file location and name. Click OK and the you can open the DBF file in Excel.
BACK to USC GIS Page
Last Updated 6/16/05