Join Operation

[flahn]

I have started to implement a join operation for spatio-temporal arrays with differing resolution. But I ran into complications, when performing a downward join (joining an image with lower resolution into a higher resolved array, in combination with differing temporal resolutions). There is need for debugging in this case.

It is mainly due to the multiple 'iquery' calls and storing of temporary arrays, what makes it difficult to debug. The basic functionality is provided, but the more complex use cases remain not debugged.

[flahn]

Overview about Use Cases:

• A and B are arrays
• upscaling is using SciDB's xgrid
• downscaling involves SciDB's regrid
• spatial() an array having a spatial reference, temporal() means temporal reference, and spatioTemporal accordingly

Case 1 Spatial Merge (S -> S)

spatial(A) -> spatial(B)
a) higher -> lower resolution (downscaling)
b) lower -> higher resolution (upscaling)

Case 2 Spatial to Spatio-Temporal Merge ( S -> ST)

spatial(A) -> spatioTemporal(B)
a) higher -> lower resolution
b) lower -> higher resolution
Note

Case 3 Spatio-Temporal to Spatio-Temporal Merge (ST -> ST)

spatioTemporal(A) -> spatioTemporal(B)
a) spatial higher -> spatial lower resolution | same temporal resolution
b) spatial lower -> spatial higher | same temporal resolution
c) spatial higher -> spatial lower resolution | temporal higher -> temporal lower
d) spatial lower -> spatial higher | temporal higher -> temporal lower
e) spatial higher -> spatial lower resolution | temporal lower -> temporal higher
f) spatial lower -> spatial higher | temporal lower -> temporal higher
g) same spatial resolution | temporal higher -> lower
h) same spatial resolution | temporal lower -> higher

Notes:

• no ST -> S merge, since the spatio-temporal array needs to be aggregated over time to be merged, therefore the user has to make individual adaptions, afterwards it will be a S -> S merge
• Join work for cases 1 and 2 pretty much and for some conditions of case 3.
• the function "equalize" will be used to prepare the arrays for merging