[GRASS-user] Linking multidimensional data to a single point

[Paulo van Breugel]

Rich Shepard <rshepard at appl-ecosys.com> schreef op 15 maart 2015 23:49:06 CET:
>On Sun, 15 Mar 2015, Andy Wickert wrote:
>
>> So to boil it down to the simplest part of what you said, the key is
>just
>> to have an ID column in the GRASS table that links to a table in a
>> database structure outside of GRASS?
>
>Andy,
>
>Yes. You can keep all point attributes in SQLite (or other rdbms)
>tables
>rather than in GRASS. 

The attribute table is in a sqlite table already, unless you are still using dbf as database backend for grass. Just link your other tables to that attribute table?


It's been a while since I last did this so the
>specifics are not immediately available. I would link each point to a
>table
>which describes it; perhaps including geographic coordinates, name, and
>other information. Then your discharge and sediment data are in other
>tables
>that are related to each row in the main table. This also allows you to
>run
>SQL queries on the data (such as descriptice statistics) outside of
>GRASS.
>
>> Just to make sure that I was clear: the problem is how to include
>multiple
>> rows of data that all correspond to just one point in GIS (so "grain
>size"
>> with frequencies in each grain size class or "discharge" with
>discharges
>> at different times).
>
> Database design is a topic of itself. Separate attribute data from the
>spatial data; the former goes into a database (multiple tables), the
>latter
>in GRASS files.
>
>In your initial message you describe three different categories of data
>and each should be in its own table. Information about each data
>collection
>point (which is seen on the map) is in one table. This could include a
>site
>ID as the primary key, site name, perhaps the stream or drainage basin
>in
>which it is located, and other information about the location itself.
>
> Your second table contains hydaulic data: sample ID (the primary key),
>station ID (which relates that row to your point), collection date and
>time,
>discharge, channel width, and any other relevant information.
>
>Your third table contains sediment data: sample ID (primary key),
>station
>ID, date and time, each grain category (e.g., silt, clay, fine sand,
>coarse
>sand, gravel, cobble), and the percentage or proportion (dry weight?)
>of
>each.
>
>You could also have additional tables if you want to store more
>categories
>of data for each point.
>
>Hope this helps,
>
>Rich
>
>
>
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