Support image metadata field for laser distances

[mzur]

biigle/volumes#55 will implement support for standardized image metadata fields. Among these is REF_laserdistances with the laser distance (in m? ask Timm). If this field is available for an image, use it during laser point detection. Offer the manual input as override but display a warning that there are metadata values present.

[tschoeni]

The fields are generally undefined to allow for various specifications (e.g. Lat/Lon in decimal degrees, or decimal minutes, etc.). With regard to the laser points it should be a distance in m in case of a two laser point setup. For three laser points (e.g. AWI OFOBS system) something else would be required. But it is not the idea of the workflow paper to define a solution for any such case. So it would be appropriate to store a tripel (0.5, 0.4, 0.5) in the REF_laserdistances to define the three distances in a laser point triangle. For systems with a moving third lp that encodes camera altitude (SUB_distance, e.g. the BGR system) you would need to define something else. The important thing from a data management perspective is that the field exists and people know where to look for any kind of information on laser points.

[mzur]

Ok, if there is no fixed specification for these fields, we will define "our" requirements in the BIIGLE manual.