From Pixels to Points
Digitizing Spatial Data
where is your data? gis.stanford.edu
about me
gis.stanford.edu
Modeling the World
Data Models
Everything is somewhere, but how do we say where?
Coordinate Systems
Geographic Coordinates
Projections
Think of them as translations from 3d to 2d
Vector Data
Vector Formats
Shapefiles*
*(a shapefile isn't really a file)
- *.shp
- *.shx
- *.dbf
- *.prj
GeoJSON
{
"type": "FeatureCollection",
"features": [
{
"type": "Feature",
"properties": {
"Label": "\"Null Island\""
},
"geometry": {
"type": "Point",
"coordinates": [
0,
0
]
}
},Hardcopy Sources
https://slides.com/staceymaples/digitizingbootcamp
"Heads-down" Digitization
On-Screen/Head's Down Digitization
"Heads-up" Digitization
Digitization
Feature Generalization
How long is the coast of Britain?
Errors
Undershoots & Overshoots
Reshaping
(smoothing & thinning)
Error Across Layers
Error Across Layers
OK, now... how webmaps work
web mercator
https://allmaps.xyz/images/45bbc7ea6e45e5c9/{z}/{x}/{y}.png
https://allmaps.xyz/images/45bbc7ea6e45e5c9/{z}/{x}/{y}.png
Credit: @chris_whong
Let's Digitize!!
Spatial Data Bootcamp - Digitizing Data
By Stace Maples
