add stream profile table

extras/profile/README.md

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+# Stream profile
+
+Extracting a stream profile and/or gradient from FWA geometries is a straightforward, but often repeated task.
+Run the required query once and materialize the result in table `whse_basemapping.fwa_stream_profiles` for re-use.
+
+## Process
+
+	./process.sh
+
+## Output	
+
+	                 Table "whse_basemapping.fwa_stream_profiles"
+	          Column          |       Type       | Collation | Nullable | Default
+	--------------------------+------------------+-----------+----------+---------
+	 blue_line_key            | integer          |           |          |
+	 downstream_route_measure | double precision |           |          |
+	 upstream_route_measure   | double precision |           |          |
+	 downstream_elevation     | double precision |           |          |
+	 upstream_elevation       | double precision |           |          |
+

extras/profile/process.sh

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+set -euxo pipefail
+
+PSQL="psql $DATABASE_URL -v ON_ERROR_STOP=1"
+WSGS=$($PSQL -AXt -c "SELECT watershed_group_code FROM whse_basemapping.fwa_watershed_groups_poly")
+
+$PSQL -c "drop table if exists whse_basemapping.fwa_stream_profiles"
+$PSQL -c "create table whse_basemapping.fwa_stream_profiles (
+  blue_line_key integer,
+  downstream_route_measure double precision,
+  upstream_route_measure double precision,
+  downstream_elevation double precision,
+  upstream_elevation double precision
+ );
+ "
+
+parallel $PSQL -f sql/fwa_stream_profiles.sql -v wsg={1} ::: $WSGS

extras/profile/sql/fwa_stream_profiles.sql

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+-- extract coordinates from streams
+insert into whse_basemapping.fwa_stream_profiles (
+  blue_line_key,
+  downstream_route_measure,
+  upstream_route_measure,
+  downstream_elevation,
+  upstream_elevation
+)
+
+with coordinates as (
+  select
+    blue_line_key,
+    downstream_route_measure,
+    linear_feature_id,
+    edge_type,
+    (st_dumppoints(geom)).path[1] as node_id,
+    (st_dumppoints(geom)).geom as geom
+  from whse_basemapping.fwa_stream_networks_sp
+  where watershed_group_code = :'wsg'
+),
+
+-- extract elevation of each point and determine distances between each point
+lengths as (
+  select
+    blue_line_key,
+    downstream_route_measure,
+    linear_feature_id,
+    edge_type,
+    node_id,
+    st_z(geom) as elevation_from,
+    st_z(lead(geom) OVER(ORDER BY blue_line_key, downstream_route_measure, node_id)) as elevation_to,
+    st_distance(geom, lead(geom) OVER(ORDER BY blue_line_key, downstream_route_measure, node_id)) as length
+  from coordinates
+  order by blue_line_key, downstream_route_measure, node_id
+),
+
+-- derive measure of at upstream point
+-- drop duplicates at geometry endpoints (where length is 0)
+-- drop the final vertex (where length is null)
+tidy as (
+  select
+    row_number() over() as id,
+    blue_line_key,
+    linear_feature_id,
+    edge_type,
+    round((downstream_route_measure + sum(length) over (order by blue_line_key, downstream_route_measure, node_id))::numeric, 2) as upstream_route_measure,
+    round(elevation_from::numeric, 2) as elevation_from,
+    round(elevation_to::numeric, 2) as elevation_to
+  from lengths
+  where length !=0 and length is not null
+  order by blue_line_key, downstream_route_measure, node_id
+)
+
+select
+  blue_line_key,
+  lag(upstream_route_measure, 1, 0) over (order by id) as downstream_route_measure,
+  upstream_route_measure,
+  elevation_from as downstream_elevation,
+  elevation_to as upstream_elevation
+from tidy;