Spatial Search - Digitizing Instructions

The Spatial Search function lets you draw an irregular area on the map and find all the sites in the atlas that fall within one kilometer of it.   Each time you click the left mouse button (not holding it down to pan) the system adds a vertex to the area of interest.  The first click adds a point; the next click adds a point and draws a line between them; the third and every later click adds a point and draws a shaded magenta polygon.  The first figure above shows a minimal, three-point polygon.  In the second picture, the cursor points to a location not in the polygon.  If you click the cursor in this place, the three-sided figure will be replaced by a four-sided figure, with its fourth vertex at the location of the mouse click.

Digitize points in one direction only, either a clockwise or counterclockwise, and do not try to add a point between two existing points; doing so will cause "bowtie" effects in the polygon shape, as shown in the third picture above.

If you need to back up, use the "Drop Last Point" button below the map.  Each time you press this button, the last point you clicked in the polygon will be removed, and the polygon will be redrawn to its earlier shape.  If you want to remove the entire polygon, and start over, press the "Reset Map" button.  When you are satisfied with the shape of the Area of Interest, press the "Submit Search" button.  

The application searches for sites that fall within the area (buffered by one km.) you digitized and draws them on Google Earth, because there are thousands of sites, and selecting a large area returns too many to plot in Google Maps.

The map will not allow searches outside the DAAHL study area, which is marked by the white rectangle.  An error message will be shown if any point you digitize is outside the rectangle.

When the map is zoomed in closely sites are shown as red dots, which can be clicked to reveal the site name in the information balloon; clicking the site name opens its information page in a new window.