Why is elevation negative?
Thank you for reaching out here. I’m happy to help out with your inquiry.
Elevations may appear negative on small maps (>30 minutes flight time). This is because we are using the drone’s take-off point as the relative elevation (0 ft). Any ground above this point will be + and anything below this point will be -.
In theory, if you have a map will a hill in it - and you take off from the top of the hill, many of the elevation values will be negative since they exist below the take-off point.
You can adjust this point’s elevation through Map Calibration: https://help.dronedeploy.com/hc/en-us/articles/1500004964022-Calibrate-Elevation
Are you talking about on the controller screen or on the map is processed? It could be that you are near a coast? Or an interior body of water? You are probably below the ellipsoid or geoid. You need a known elevation on site to know how to adjust the single point as Lindsey mentioned.