Hi,
This seems to be quite simple but I'm having a hard time trying to get what I
want. The thing is that I have several lines and I'm trying to interpolate them
and then extract the points to a CSV file for example. I'm still stuck in the
interpolation step. This is what I have so far:
whole table:
mydb=# select id,profile,dist_dd,seg_fldr from smoothnav_line_wgs84 order by id;
id | profile | dist_dd | seg_fldr
----+--------------------+--------------+----------
1 | 5148P-LF | 0.0010699943 | 245
2 | 5745P-LF | 0.0015981060 | 282
3 | 5920P-LF | 0.0012989445 | 295
4 | 0053P-LF | 0.0013805557 | 304
5 | 0233P-LF | 0.0012318259 | 278
6 | 0416P-LF | 0.0012958645 | 287
7 | 0601P-LF | 0.0011592394 | 227
8 | 0729P-LF | 0.0013005116 | 328
9 | 0946P-LF | 0.0012521930 | 239
10 | 1119P-LF | 0.0013112367 | 300
11 | 1258P-LF | 0.0013001241 | 254
12 | 1434P-LF | 0.0012408036 | 269
13 | 1622P-LF | 0.0010311844 | 225
14 | 1800P-LF | 0.0009614843 | 229
15 | 1927P-LF | 0.0011774532 | 247
16 | 2103P-LF | 0.0011027050 | 243
17 | 2236P-LF | 0.0011613916 | 231
18 | 2410P-LF | 0.0010903102 | 254
19 | 2546P-LF | 0.0011652277 | 227
20 | 2722P-LF | 0.0010217751 | 246
21 | 2903P-LF | 0.0010245117 | 225
22 | 3056P-LF | 0.0011750912 | 283
23 | 3240P-LF | 0.0010244741 | 209
24 | 3403P-LF | 0.0012303394 | 302
25 | 3550P-LF | 0.0011860473 | 246
26 | 3733P-LF | 0.0013065220 | 299
27 | 3922P-LF | 0.0011613916 | 232
28 | 4213P-LF | 0.0027780243 | 588
29 | 4517P-LF | 0.0027969726 | 629
30 | 4831P-LF | 0.0028498347 | 571
31 | 5146P-LF | 0.0029280876 | 633
32 | 5459P-LF | 0.0028549158 | 551
33 | 5823P-LF | 0.0028575039 | 597
34 | 0124P-LF | 0.0029464684 | 616
35 | 0436P-LF | 0.0029445455 | 609
36 | 0808P-LF | 0.0029842086 | 592
(36 rows)
one row for tests:
mydb=# create table test1 as select * from smoothnav_line_wgs84 where id=1;
now, to generate points along the line in test1 I need the distance between
points, so this is the dist_dd/(seg_fldr-1). In the id=1 above would be:
0.0010699943/(245-1) = 0.000004385222540983606557, so, I can get this like:
mydb=# select dist_dd/(seg_fldr-1) from test1 ;
?column?
----------------------------
0.000004385222540983606557
(1 row)
so far so good, here it comes the problem, I need to get 245 points from my
line, this is starting from the actual origin and putting a point every
0.000004385222540983606557 decimal degrees, so at the end I should come up with
245 points instead of 49 points (because the current geom is actually composed
of only 49 points), so I really think my command line doesn't reflect what I
want, but it's what I'm trying to figure it out:
mydb=# select st_line_interpolate_point(geom,(dist_dd/(seg_fldr-1))),
generate_series(1,max((seg_fldr)::int)) from test1;
and I'm getting this error: ERROR: column "test1.geom" must appear in the
GROUP BY clause or be used in an aggregate function
I keep reading but perhaps this is too advanced to my sql understanding. Any
help will be really appreciated.
Thanks,
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