Interpolate beach attributes along coastlines to visualize the values:
 

In each case, the data is stored in vector coverage (point coverage) of Maui_Beaches.vct Before any analysis, create attribute value file for each attribute.  For example, the attribute value file for board-surfing was exported from database workshop (the first field is IDRI_ID, and second field is Board_Surfing ). This board_surfing.avl file allows to assign appropriate values to each point feature from the point coverage during interpolation process.  This is analogous to using spot heights when interpolating a DTM.

Use surface analysis INTERPOL, creating new image file for ouput, distance weight exponent of 5.0 (to make peaks small), use attribute value file for heights, output data type Real, 1000 x 1000 raster image, and adjust output file extent by 5000 m in every direction.  Use larger bounds for output raster image than input image (extrapolate a little - helps in visualization).  To be consistent, use the same x,y extent for each raster image from this process:

To display results, each image was multiplied by an image of coastlines where land surface of Maui and a buffer around coastline (inclusive) has cell values of 1 and over ocean surfaces away from land cell values of 0.  This overlay operation results in the ocean surface with values of 0 and can be assigned background color for display.  This image is then combined in a map composition with a vector layer for coastlines and solid fill for land surface.  In result, only a narrow band of area outside the coastline remains with values from the analysis, showing more realistic results. The overall cartographic model is:

Beach attributes
 

Fore each beach attribute, click on attribute to view image with results of analysis	Description of results
Board-surfing (surfing)	The best board surfing is on the north shore, just east of Kahului.  Other good spots are in N.W. part of the island, and south-west of Lahaina.  Most of the coasts are inaccessible or too dangerous for board surfing.  However this analysis includes only surfing spots near beaches, so there should be more surfing areas than shown in this map.
Body-surfing (boogie boarding)	(have data but not analysed - similar to swimming and surfing attributes)
Wind-surfing	The only good spot for windsurfing is north and east of Kahului.  It is possible to windsurf at other locations but it is far worse there.
Snorkelling / Diving	This distribution is highly variable and specific to each point feature on the coast.  Interpolation for coastlines does not make sense here.  Instead, use graduated-point symbol map.
Swimming	Swimming is best on west coasts of Maui and near Hana on east coast.
Sand quality	This map is a good approximation of sand quality of Maui coastlines because sand occurs only on beaches.  The best sand is found where most tourist resorts are found, which is in the south-west part of the island.
Water quality	(not analysed - most beaches similar)
Storm wave height	(not analysed - some inconsistencies - waes high at most beaches during storms)
Water safety (surf break, waves, currents)	The safest shores tend to be on the south-east coastlines where wave action is much less than on the north shore.  Some beaches are more protected than others.
Seclusion  (city beach to wild beach)	Almost the opposite of beach access, but there are exceptions.
Access  (trail, dirt road, road,highway)	This is an excellent image that shows the accessibility of beaches on Maui.

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