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

[Andy Wickert]

On Sun, Mar 15, 2015 at 11:49 PM, Rich Shepard <rshepard at appl-ecosys.com>
wrote:

> 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. 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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Hi Rich,

This helps very much and learning how to do this will be high on my to-do
list. Thank you!

Andy
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