Add a graticule

In order to accurately indicate the location of each place on the earth, people assume a coordinate system for the earth's surface, which is the latitude and longitude coordinate system.

On maps and globes, we can see thin lines, some horizontal and some vertical, which are the longitude and latitude. The warp and weft are intertwined, much like the squares on a chessboard, forming a warp and weft network.

According to these longitude and latitude lines, the position and direction of any place on the ground can be accurately determined. Using the longitude and latitude marked on it, various locations, regions and various geographic locations on the earth's surface can be determined. It is useful in military, aviation, navigation, etc. For example, a ship is sailing on the vast sea, and an airplane is flying in the vast sky. No matter where you go, people can use instruments to accurately measure its latitude and longitude to determine its position.

View examples

In MapServer, latitude and longitude lines can be drawn on the map according to its cartographic capabilities. This feature is a latecomer, originally developed by John Novak in 2003. The drawing of graticules is almost necessary for desktop mapping to facilitate location determination when reading maps; however, it is not necessary for WebGIS. WebGIS enhances the user's operations on the map, and the latitude and longitude coordinates can be quickly obtained through the spatial query function.

The image below is an example, drawn on a map with latitude and longitude lines, with the longitude and latitude of the longitude lines drawn to the ends of the line.

Here is its Mapfile :

01 MAP
02     IMAGETYPE "PNG24"
03     EXTENT -180 -90 180 90
04     SIZE 600 300
05     SHAPEPATH "/gdata"
06     IMAGECOLOR 255 255 255
07     FONTSET "../fonts/fonts.list"
08     SYMBOLSET "../symbols/symbols35.sym"
09     LAYER
10         NAME "topo"
11         DATA "land_shallow_topo_8192.tif"
12         STATUS OFF
13         TYPE RASTER
14         PROCESSING "BANDS=1,2,3"
15         OFFSITE 71 74 65
16     END
17     LAYER
18         NAME "states_line"
19         DATA "wcountry.shp"
20         STATUS OFF
21         TYPE LINE
22         CLASS
23             NAME "State Boundary"
24             STYLE
25                 SYMBOL "line5"
26                 COLOR 255 255 0
27                 SIZE 1
28             END
29         END
30     END
31     LAYER
32         NAME "grid"
33         METADATA
34             "description" "Grid"
35         END
36         TYPE LINE
37         STATUS ON
38         CLASS
39             NAME "Graticule"
40             COLOR 0 0 0
41             LABEL
42                 COLOR 255 0 0
43                 FONT "arial-bold"
44                 TYPE TRUETYPE
45                 SIZE 8
46                 POSITION AUTO
47                 PARTIALS FALSE
48                 BUFFER 2
49                 OUTLINECOLOR 255 255 255
50             END
51         END
52         PROJECTION
53             "init=epsg:4326"
54         END
55         GRID
56             LABELFORMAT DD
57         END
58     END
59 END

Code modification

Compared with the previously released image map, the code changes are as follows: