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

[Andy Wickert]

On Sun, Mar 15, 2015 at 4:08 PM, Rich Shepard <rshepard at appl-ecosys.com>
wrote:

> On Sun, 15 Mar 2015, Andy Wickert wrote:
>
>  EXAMPLE 1:
>>
>> I want to present a time series of stream gage data. I would like a data
>> table to have:
>>
>> time     water_discharge_m3_s     sediment_discharge_m3_s
>>
>> And to have an entire time series of values for a given grass vector
>> category (i.e. vector point, in this case).
>>
>
> Andy,
>
>   This is a typical database table. Each row needs a unique ID. What I do
> for all my environmental databases would be something like this:
>
> CREATE TABLE Discharges (
>   site VARCHAR(30),
>   sampdate DATE,  -- or use TIMESTAMP to have date and time in a single
>   samptime TIME,  -- field.
>   h20disch REAL,
>   seddisc REAL,
>   PRIMARY KEY (site, sampdate, samptime)
> )
>
>   Then assign your points to the site column.
>
>  EXAMPLE 2:
>>
>> I have a series of data on sediment composition at a river site. For each
>> point, I want to have a 2D data table with multiple values for:
>>
>> grain_size     lithology
>>
>
>   This would have a similar table structure. Columns (attributes) would
> include sediment sample ID (the table's primary key that refers to a table
> of sediment samples by location, date, and time), grain size, and
> lithography.
>
>   From a statistical analytic point of view I would look at each sample as
> a
> composition and apply models suitable for compositional data analysie
> (CoDA)
> to them. CoDA was developed by geochemists and is appropriate for your
> data.
>
> HTH,
>
> Rich
>
-- 
> Richard B. Shepard, Ph.D.
> Applied Ecosystem Services, Inc. |             Troutdale, OR 97060 USA
> www.appl-ecosys.com      Voice: 503-667-4517         Fax: 503-667-8863
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>


Thanks Rich,

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? 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).

Best,

Andy
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