[Mapserver-users] problems | postgis, projection, extent

[Leah Roderman]

I seek the wisdom of the masses: I do not seem to have my mapfile configured properly. (Or, I need to adjust my understanding of what I am seeing.) There's a lot of detail in here, but I figure more is better...

I am running MapServer 3.6.4 (OUTPUT=PNG OUTPUT=JPEG OUTPUT=WBMP SUPPORTS=PROJ SUPPORTS=TTF SUPPORTS=WMS_SERVER INPUT=TIFF INPUT=EPPL7 INPUT=JPEG INPUT=POSTGIS INPUT=GDAL INPUT=SHAPEFILE) on RedHat8.0 using PostGIS 0.7.4 and Postgres 7.3.2.

I successfully ran the demo and proceeded to create my own mapfile using data from CaSIL. The map was visible, I could identify county and water polygons. Then I introduced a layer with connectiontype postgis, which led to a round of debugging and testing to confirm that the db is indeed being connected to.

Problem #1: PostGIS layer produces a single dot (roughly in middle of box) which is not at the correct coordinates in relationship to the other layers. (Coordinates for S.F., CA but dot is hovering around Mammoth.) I am using filter, expression, symbol (see mapfile below). Tried adding additional expressions and changing query but the dot does not respond. Actually, I can make it change color and size, but it won't budge an inch.

So I thought about it...maybe I needed to use projection. After all, my data from CaSIL is Albers/NAD 27 in meters, and my geocoords stored in Postgres are lat/long NAD27...?

Problem #2: After adding projection to map object and each layer object, now all I see is a nice empty box of background color. I'm guessing I compounded problem #1 by tinkering with projection, and now I have two problems.

Here's an example of coordinates I have in a geometric column (used GeometryFromText to insert) in my db that I want to pull out and display on a layer:

SRID=-1;POINT(36.396331 -119.020059)

I can make the postgis layerconnection choke (change to user without grant) to see mapserver's query:

SELECT address_id::text,asbinary(force_collection(force_2d(mat_coord)),'NDR'),OID::text from addr_match WHERE (address_id = 11407) and (mat_coord && setSRID( 'BOX3D(-311074.95303064 -333852.22957132,71688.72916536 212953.03070868)'::BOX3D,find_srid('','addr_match','mat_coord') ));

and run it from psql command line to confirm that query returns something:


 address_id |                           asbinary                           |   oid
------------+--------------------------------------------------------------+----------
 11407      | 010700000001000000010100000057790261A7E2424095456117459C5EC0 | 36035143


I've beat on this for a couple of days and trolled the archives, but I haven't found an answer yet. (It's probably something completely obvious that I'm missing, that would be Great.) If problem #1 rings any bells, please let me know -- not sure if it's a MapServer or a PostGIS issue. As for problem #2, I'm likely better off just solving one thing at a time, but I'd love some links to explanations of projection and extent. (I'm geography and cartography deficient, so though I understand the concept of a coordinate system, and projection as a means of selecting which distortion for sphere --> flat, the relationship between these and extent and imagesize gets my head fuzzy.)

Anyway, here's my mapfile that produces problem #1:

# map object
NAME CACO
STATUS ON
# attempted ratio to match extent
SIZE 700 1000
# derived extent from co100 using shpdump
EXTENT -373886.881 -604696.000 340099.435 449894.875
UNITS METERS
SHAPEPATH "shapedata"
IMAGECOLOR 154 179 220
SYMBOLSET "geo.sym"

# web object
WEB
  HEADER geo_header.html
  TEMPLATE geo.html
  FOOTER geo_footer.html
  LOG "mapserver.log"
  METADATA
    WMS_TITLE "Test Geo"
    WMS_ABSTRACT "This is a test"
    WMS_ACCESSCONSTRAINTS none
    WMS_ONLINERESOURCE "http://www.kinakuta.com/geoenergy/geo_init.html"
  END
END

# CaSIL CA counties
LAYER
  NAME "COUNTY"
  DATA co100a
  STATUS DEFAULT
  TYPE POLYGON
  CLASSITEM "NAME"
  CLASS
    NAME "Alameda"
    EXPRESSION "ALAMEDA"
    COLOR 222 231 243
    OUTLINECOLOR 0 0 0
  END # class
  CLASS
    NAME "Contra Costa"
    EXPRESSION "CONTRA COSTA"
    COLOR 214 183 169
    OUTLINECOLOR 0 0 0
  END # class
  CLASS
    NAME "San Francsco"
    EXPRESSION "SAN FRANCISCO"
    COLOR 208 200 225
    OUTLINECOLOR 0 0 0
  END # class
  CLASS
    EXPRESSION /./
    COLOR 193 214 180
    OUTLINECOLOR 128 128 128
  END # class
END # layer

# CaSIL CA Hydro
LAYER
  NAME "CAHYDRO"
  DATA hydrpola
  STATUS DEFAULT
  TYPE POLYGON
  CLASSITEM "STATECODE"
  CLASS
    NAME "HYDRO"
    EXPRESSION "1"
    COLOR 154 179 220
    OUTLINECOLOR 0 0 0
  END # class
END # layer

# postgis addr_match
LAYER
 CONNECTIONTYPE postgis
 NAME "PLANTS"
 CONNECTION "user=myuser dbname=mydb"
 DATA "mat_coord from addr_match"
 STATUS DEFAULT
 TYPE POINT
 FILTER "address_id = 11407"
 CLASS
   EXPRESSION ([address_id] = 11407)
   SYMBOL "circle"
   COLOR 255 1 3
   SIZE 60
 END # class
END # layer

END # map



-----------------

and for anyone interested in problem #2, I added this to the map object:

PROJECTION
    "proj=aea"
    "lat_1=34.0"
    "lat_2=40.5"
    "lat_0=0"
    "lon_0=-120"
    "x_0=0"
    "y_0=-4,000,000"
    "datum=NAD27"
END

and this to each layer:

  PROJECTION
    "proj=aea"
  END

...but I didn't change extent or anything else. I derived projection from my CA Counties layer, which contains a text file with this information:

  VITAL STATISTICS:

  Datum:                       NAD 27
  Projection:                  Albers
  Units:                       Meters
  1st Std. Parallel:           34 00 00 (34.0 degrees N)
  2nd Std. Parallel:           40 30 00 (40.5 degrees N)
  Longitude of Origin:         -120 00 00 (120.0 degrees W)
  Latitude of Origin:          00 00 00 (0.0 degrees)
  Latitude of Origin:          00 00 00
  False Easting (X shift):     0
  False Northing (Y shift):    -4,000,000


thank you all in advance,

- Leah

p.s. neither problem produces anything in my logfiles for mapserver or psql or apache