projections Property

Vega projections map longitude and latitude data to projected x and y coordinates. When working with geospatial data in OmniSci, you can use projections to define geographic points and regions.
General projections property JSON format:
1
"projections": [
2
       {
3
         "name": "<projectionName>",
4
         "type": "<projectionType>",
5
         "bounds": {
6
               "x": [<minLong>,<maxLong>],
7
               "y": [<minLat>,<maxLat>]
8
         }
9
       }
10
]
Copied!
When you specify a projection, you must reference it in the Marks Property using the transform object. For example, if you define the projection my_mercator_projection:
1
"projections": [
2
{
3
   "name": "my_mercator_projection",
4
   "type": "mercator",
5
   "bounds": {
6
     "x": [-120.0, 120.0],
7
     "y": [-20.0,20.0]
8
   }
9
 }
10
 ]
Copied!
you then reference it as follows:
1
"marks": [
2
{
3
   "type": "symbol",
4
   "from": { "data": "fec_contributions_oct" },
5
   "properties": { ... elided ... }
6
   "transform": {
7
      "projection": "my_mercator_projection"
8
   }
9
 }
10
 ]
Copied!
The projections specification has the following properties:
Property
Data Type
Required
Description
name
string
X
User-assigned name of the projection.
type
string
X
Projection type. Currently supported types:
mercator: Mercator map projection.
bounds
object
​
Specifies the longitude and latitude bounding box for the projection. Default values:
x: [-180.0, 180.0]
y: [-85.0, 85.0]
Example
Use Vega projection projection alongside array columns:
1
{
2
      "width": 1024,
3
      "height": 1024,
4
      "data": [
5
              {
6
                      "name": "table",
7
                      "sql": "SELECT rowid, coords[1] as x, coords[2] as y FROM cities WHERE coords[1] BETWEEN $minLon AND $maxLon AND coords[2] BETWEEN $minLat AND $maxLat"
8
              }
9
      ],
10
      "projections": [
11
      {
12
              "name": "projection",
13
              "type": "mercator",
14
              "bounds": {
15
              "x": [-120.0, 120.0],
16
              "y": [-20.0, 20.0]
17
              }
18
      }
19
      ],
20
      "scales": [
21
      ],
22
      "marks": [
23
              {
24
                      "type": "symbol",
25
                      "from": {"data": "table"},
26
                      "properties": {
27
                              "shape": "circle",
28
                              "xc": {
29
                                      "field": "x"
30
                              },
31
                              "yc": {
32
                                      "field": "y"
33
                              },
34
                              "fillColor": "darkblue",
35
                              "width": 25,
36
                              "height": 25
37
                      },
38
                      "transform": {
39
                              "projection": "projection"
40
                      }
41
              }
42
      ]
43
}
Copied!

data Property

scales Property

Last modified 2yr ago

Export as PDF

Copy link

Contents

Example