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"

    add_object_three-line.png

Fill in the attributes for the shape, such as name and comments. You can click the Color or Style icon or select an option for Line Weight or Line Opacity to change the appearance of a line. You can click the Color icon or
select an option for Line Weight, Line Opacity or Polygon Fill to change the appearance of a Polygon.

line_and_polygon_appearance_attributes.png

When you have finished updating the attributes you are ready to draw the shape. Click "OK" and you can begin drawing. Alternatively you can begin drawing before clicking "OK". In this case, once you double-click to finish the shape the attribute dialog will close and 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.

click_to_draw.png

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.

    drawing_straight_continuous.png

  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.

    snapto_menu.PNG

    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.)

    snapto_steps.png

    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.

vertext1.png

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

vertex2.png

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

online_vertex.png

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:.

    right-click-line-expanded.png

    right-click-polygon-expanded.png

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

    left-click-line-polygon.png

    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.

    click_line_name.png

    click_polygon_name.png

Specialized Lines and Polygons

Adding the following objects will generate specialized lines / polygons. Once created they can be modified and edited like any other line / polygon.

  1. Buffer - creates a polygon as a given buffer on all sides of a given line or polygon
  2. Bearing Line - creates a line given: the starting point, bearing, and length of line
  3. Range Ring - creates lines in the shape of circles given the center and radii.
  4. Sector - creates a sector (section of a circle) as a polygon, given: the center point, two bearings and a start and end radius

Create a Buffer Polygon

A buffer polygon is polygon created by specifying a buffer distance and then drawing the base line (or polygon). The resulting polygon has a buffer the specified distance from all points on the base line (or polygon). You can create a buffer polygon as follows:

  1. Initiate the buffer tool using any of the following methods:

    1. Selecting the “Add” menu on the top bar and then "Add Buffer"
    2. Or selecting “Add New Object” at the bottom of the left menu bar and then "Add Buffer"
    3. Or right-click a location on the map, click "New", then "Buffer".
  2. A dialog prompts you for the buffer distance, and whether the distance is in feet or meters. Specify the desired buffer distance and click "OK".

    buffer1.png

  3. The standard polygon dialog will open. Fill in the attributes and draw a line (or polygon).

    buffer2.png

  4. A polygon will be created with the given buffer around the drawn line (or polygon):

    buffer3.png

Create a Bearing Line

A bearing line is a line that starts at given coordinates and points in a given direction for a given length. You can create a bearing line as follows:

  1. Initiate the bearing tool using any of the following methods:

    1. Right-click the start of the bearing line on the map, click "New", then "Bearing Line". Start of bearing line defaults to the point you clicked.
    2. Or selecting “Add New Object” at the bottom of the left menu bar and then "Add Bearing Line". Start of bearing line defaults to center of the map.
    3. Or selecting the “Add” menu on the top bar and then "Add Bearing Line". Start of bearing line defaults to center of the map.
  2. Fill in the attributes:

    bearing1.png

    1. Label: Name of the bearing line
    2. Coordinates: The starting point of the bearing line. The coordinates default to either the point that was right-clicked or the center of the map, depending on how the bearing line tool was initiated. You can change the coordinates to specify a different starting point.
    3. Color and Style: If desired, click the Color or Style icon to change the appearance of the bearing line.
    4. Bearing: The bearing of the line. Can be specified as a true bearing or adjusted for magnetic declination.
    5. Select "true" ( bearing is relative to true north) or "mag" (bearing is relative to magnetic north)
    6. Range: The length of the bearing line. Can be specified in meters or miles.
    7. Select "miles" or "meters".
  3. Click "Create".

  4. The following example was created with the above attributes.

    bearing2.png

Create Range Ring(s)

You can create one or more rings at the same time, all centered on the same point. Create range ring(s) as follows:

  1. Initiate the Range Ring tool using any of the following methods::

    1. Right-click the center of the range ring(s)on the map, click "New", then "Range Ring". Center of ring defaults to the point you clicked.
    2. Or selecting “Add New Object” at the bottom of the left menu bar and then "Add Range Ring". Center of ring defaults to center of the map.
    3. Or selecting the “Add” menu on the top bar and then "Add Range Ring". Center of ring defaults to center of the map.
  2. Fill in the attributes:

    range_ring1.png

    1. Coordinates: The center of the range rings. The coordinates default to either the point that was right-clicked or the center of the map, depending on how the range rool tool was initiated. You can change the coordinates to specify a different center of the range rings.
    2. Enter one or more radii of each range ring, separated by commas.
    3. Select "miles" or "meters".
  3. Click "Create". The rings are created as circular lines and appear in the “Lines and Polygons” folder.

  4. The following example was created with the above attributes.

    range_ring2.png

Create a Sector Polygon

Create a sector (section of a circle) as a polygon as follows:

  1. Initiate the sector tool using any of the following methods:

    1. Right-click the center of the sector on the map, click "New", then "Sector". Center of sector defaults to the point you clicked.
    2. Or selecting “Add New Object” at the bottom of the left menu bar and then "Add Sector". Center of sector defaults to center of the map.
    3. Or selecting the “Add” menu on the top bar and then "Add Sector". Center of sector defaults to center of the map.
  2. Fill in the attributes:

    sector1.png

    1. Coordinates: The center of the circles defining the sector. The coordinates default to either the point that was right-clicked or the center of the map, depending on how the sector tool was initiated. You can change the coordinates to specify a different center of the sector.
    2. Color and Fill: If desired, click the Color icon or select an option for Fill to change the appearance of the sector.
    3. Bearing: The bearing of the straight sides of the sector. The second bearing is clockwise to the first bearing. Can be specified as a true bearing or adjusted for magnetic declination
    4. Select "true" ( bearing is relative to true north) or "mag" (bearing is relative to magnetic north)
    5. Range: The radius of the inner and outer circles defining the circles. Can be specified in meters or miles. Specify one or both ranges. If both ranges are specified, the resulting sector will look like a slice of a donut. If only one is specifed, or one is zero, the resulting sector will look like a slice of a pie.
    6. Select "miles" or "meters".
  3. Click "Create".

  4. The following example was created with the above attributes. The sector is blue, the red arrows illustrate the attributes.

    sector2.png

  5. Here are more examples, including a pie shape, a solid circle and a donut:

    sector_examples.png

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.

    resample.png

    • 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.

    convert_line_to_polygon.png

    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.

    convert_polygon_to_line.png

  • 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".

    create_points.png

    Markers are created along the line at the specified interval.

    milemarkers.png

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.

    reverse_line.png

  • 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”.

      join_line.png