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

[Rich Shepard]

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