Lines and Polygons

Creating Lines and Polygons

You can add a Line or Polygon by:

  1. Selecting the “Add” menu on the top bar and then "Add Line" or "Add Polygon",

  2. Or selecting “Add New Object” at the bottom of the left menu bar and then "Add Line" or "Add Polygon"

  3. Or right-click a location on the map, click "New", then "Line" or "Polygon"


Fill in the attributes for the shape, such as name and comments. If desired, click the Color and/or Style icon to change the appearance of the shape.


When you have finished updating the attributes (do not click 'OK') you are ready to draw the shape. Once you finish drawing the shape, the object will be saved.

Drawing Lines and Polygons

You may see this quick tip on the screen briefly before you begin to draw. See below for a more detailed description of the various drawing functions.


There are three drawing modes, you can switch back and forth between all three modes.

  1. Straight line segments: Single click begins a new straight line segment. A subsequent click will draw a line segment between the two points. Repeat as needed to complete the line.


  2. Freehand drawing: If you hold the shift key down while holding the mouse button down, you can draw the next line segment with the cursor. You do not need to continue to hold the shift key down while you are drawing. To switch back to a straight line segment, click again without holding the shift key down.

  3. “Snap to” drawing: (aka “Auto Routing”). When in drawing mode, a “Snap To” drop-down menu will appear in the upper right.

    Select "Lines" to snap to another line or polygon on the map, “OSM” for Open Street Maps, “USFS” to snap to Forest Service features and “Hydro” to snap to Hydrology features (streams, rivers and bodies of water). Note that in SARTopo Offline, the "Lines" option is the only one available. The line features available to snap-to will be highlighted in yellow.


    To draw a line along a snap-to feature, hover the cursor over a line feature, the feature will highlight in the new line or polygon's color. Click at the desired starting point for your line segment. Now hover the cursor where you want your line segment to end on the feature and the feature will turn the color of the object between the starting and ending point. (If it does not turn color, either your starting point or ending point may not be exactly on the feature.)


    Click at the ending point. You can now snap-to an intersecting line feature or use one of the other drawing modes. Note that some line features may appear to intersect but do not and you may have to bridge between them using the straight line or continuous drawing modes.

Press ESC to undo the previous line segment. This can be done repeatedly. Pressing ESC after the first click will let you start the object over again.

Double-click to finish drawing the object. If the object is a polygon, double-click will close the polygon

Editing and Deleting Lines and Polygons

Refer to Working with Objects for how to edit the attributes of or delete a line or polygon.

When editing the attributes of a line or polygon, you can also edit its shape. On the map, you will see the vertices of the shape as solid circles. In between each pair of solid circles, there will be a transparent circle.

Click and drag the solid vertices to move them.


Click and drag a transparent circle to create a new vertex.


You can delete a vertex by clicking it to select it and then pressing the delete key.

Additional features in the online version of CalTopo:

  • You can right click the vertex and choose to delete it.
  • An Undo Arrow will appear after you change a vertex or create a new one. Click it to undo the change


There are additional tools for modifying a shape described in the next section.

Line and Polygon Tool Menus

There are three methods to bring up a tools menu for a line or polygon object.

  1. Right-click the object on the map:.



  2. Or left-click the object on the map and get the object's pop-up.


    Note the length of the line and the area of the polygon appear below the object's name.

  3. Or click the object name in the left menu bar to get the object's pop-up.



Tools for Lines and Polygons

  • Profile --- Display terrain profile of a line or the perimeter of a polygon, accessible via right-click / "Profile" or the object pop-up. More detailed information is here.

  • Terrain Statistics / Stats --- Display elevation, slope, aspect, tree and land cover data for a line or the interior of a polygon. Accessible via right-click / "Stats" or the object pop-up as "Terrain Stats". More detailed information is here.

  • Print Map --- Print a map with just this line or polygon, Accessible via the object pop-up.

  • Resample --- Resamples the lines of the object and generates a new set of vertices. (Caution: This can change the shape of the object, so you may want to copy the object first. Refer to the "Convert" tool below). Accessible via right-click / "Modify" / "Resample" or the object pop-up.


    • Select whether to resample based on distance or number of waypoints.
    • If distance, enter the distance between waypoints and whether meters, feet or miles
    • If number of waypoints, enter the number of points.
    • Click “Resample”
  • Convert --- Convert or copy an object. Accessible via right-click / "Convert". A "Copy" will create a second object, the "Convert" will take the current object and convert it to the new type. Options are:

    • Copy as Line
    • Copy as Polygon
    • Convert to Line
    • Convert to Polygon

    Converting a line to a polygon will connect the first and last vertex of the line to create a polygon.


    Converting a polygon to a line will convert the perimeter of the polygon to a line, with the endpoints of the line at the point where the polygon was originally closed.


  • Create Points --- Create markers at given intervals along the line. Accessible via right-click / "Modify" / "Create Points"

    • Enter the distance and measurement unit between each point and the prefix to use when creating markers.
    • Click "Resample".


    Markers are created along the line at the specified interval.


Additional Tools for Lines

  • Extend --- Continue drawing a line from either end of the line. Accessible via right-click / "Modify" / "Extend" or the object pop-up

    • Click where you want to start the line extension. It doesn’t have to be right at the end of the line, because the program will connect your starting point to the nearest end of the original line.
    • Continue drawing the line as above.
  • Reverse --- Reverse the order of the vertices in the line. This is useful when using a directional arrow style, it will also effect the Profile of the line. Accessible via right-click / "Modify" / "Reverse Order" or the object pop-up.


  • Split --- Split the line at the cursor position.

    • Place the cursor where you want to split the line.
    • Either right-click the line and choose "Modify" / "Split Here" or left-click the line and choose "split"
    • Click “OK” to confirm the split location
    • Two lines with the same name and attributes will be created from the original line
  • Join --- Join this line with another. Accessible via right-click / "Modify" / "Join With" or the object pop-up

    • Select the join tool for the first line.
    • A dialog with a list of all of the other named lines on the map will appear. Note that you can only select lines that have been named. Select the one you want to join with the first line and click “Join”.