Embedded Files
TABLE OF CONTENTS
Parse a GeoJSON
Parse a GeoJSON
Example GeoJSON files are provided in GeoJSONExamples class, in "geojson examples" protocol.
You can parse your GeoJSON file as a string, and obtain generated object model, using "GeoJSONReader class >> fromString:".
GeoJSONReader fromString:(GeoJSONExamples barsLilleGJ).
You can parse your GeoJSON file giving an URL as parameter, using "GeoJSONReader class >> #fromURL:".
GeoJSONReader fromURL: 'https://raw.githubusercontent.com/gregoiredavid/france-geojson/master/departements/59-nord/departement-59-nord.geojson'.
Note: you can also parse a KML file by loading KML parsing project here.
Inspect object model
Inspect object model
Once you obtain your OGCObject (a FeatureCollection, a Feature or a Geometry), you can inspect and visualise it at the same time.
Visualise
Visualise
The OGCObject inspector contains 2 added tabs: "Map" & "Map with Tiles".
"Map" inspector tab renders a visualisation of geometries.
"Map with Tiles" inspector tab renders a visualisation on a map background.
Both tabs compute the most suitable zoom level to be displayed in a space of 3x2 tiles = 768x512 px.
"Map" tab
"Map with Tiles" tab
You can also visualise your model in an independant way with: "OGCViewerMorph>>#displayObject:". You can combine it with "OGCViewerMorph class>>#withMapTiles:" to custom your display settings.
Display feature information
Display feature information
If you click on a feature on a visualisation, a window appears with :
the detail of associate properties
a button to inspect clicked feature
After clicking on feature
[TO DO] Zoom + move map
[TO DO] Zoom + move map
Perform operations
Perform operations
You can call analysis methods like intersection, inclusion, length, etc, ... detailed in Simple Feature Access specifications.
More information about spatial reference system's operations in OGC-Pharo model page.
Geometrical operations
Geometrical operations
We consider that geometries are located in the same plane.
Spatial reference system package to use: OGC-Geometry
Spatial reference system class to use: OGCGeometricProjection
Spherical operations
Spherical operations
We consider that geometries are located on Earth as a perfect sphere with ray of 6372.795477598 km.
Spatial reference system package to use: OGC-Spheric
Spatial reference system class to use: OGCSphericSystem
About styling
About styling
There are several ways to custom geospatial objects appearance.
For now, you can edit:
filling color with fill
fill opacity with fill-opacity
stroke color with stroke
stroke width with stroke-width
Default style
Default style
Default style is set in the "style" protocol of OGCGeometry class:
default filling color: white for Polygons
default fill opacity: 0.5 for Polygons
default stroke color: red
default stroke width: 2
Apply a global style with GeoJSON integration
Apply a global style with GeoJSON integration
A custom style can be directly found in GeoJSON file, in the 'geometry' dictionary of a feature, alongside type and coordinates. Style must be a dictionary of strings using following keys: "fill", "fill-opacity", "stroke" and "stroke-width".
"GeoJSONExamples class >> #aMultiPolygonGJ" is a great example of style integration to GeoJSON.
GeoJSONExamples class >> #aMultiPolygon: example execution
Apply a global style with a method
Apply a global style with a method
You can obtain the same result using "OGCObject >> #applyStyle:" method. This method takes a dictionary as argument, with proper style keys and values as if they were integrated to GeoJSON.
You can generate an appropriate dictionary with "OGCObject class >> #createStyleDictionary:" method, which takes an array with the four string values in following order: #( <fill> <fill-opacity> <stroke> <stroke-width>). For example: #('orange' '0.6' 'black' '2').
Write "nil" if you don't want to change one of given parameters. For example, #('green' nil nil nil) will only change filling color, and keep default values for other style parameters.
This is an example applied on "GeoJSONExamples class >> #aMultiPolygon":
#applyStyle: method execution
Apply a style with feature conditions with a method
Apply a style with feature conditions with a method
You can decide to change the appearance of some features according to custom rules.
To apply a style under conditions, you can call "OGCObject>>#applyStyle:ifFeature:" method.
This method takes:
first, a style dictionary - as seen in previous paragraph
then, a block closure which takes a feature as variable and defines conditions that the features should respect to get given style applied
NOTE: to run the following example, you need to load NeoCSV
To study an example with metropolitan French regions, launch
"GeoJSONExamples class>>#regionsFranceMetropoleApplyStyleIfPopulation"
It displays French regions with a different color according to the number of inhabitants:
red if regional population > 10 000 000 inhabitants
orange if regional population > 5 000 000 inhabitants
green otherwise
#applyStyle:ifFeature method execution with the coloration of metropolitan French regions according to their population(numerical data source: https://www.insee.fr/fr/statistiques/1893198)
Apply a style with feature conditions with a CSV data file
Apply a style with feature conditions with a CSV data file
You can load a CSV file with practical data to use for styling!
It's a way easier and faster than coding a condition block closure with the method we present above.
You have 3 different styling types.
[ TO DO ] Classification with tags
[ TO DO ] Classification with tags
A given color is applied when the value of a given property equals to a given tag
[ TO DO ] Classification with numbers
[ TO DO ] Classification with numbers
A color is applied when the value of a given property is found in a range of given numerical values
Continuous coloration with numbers
Continuous coloration with numbers
The opacity changes proportionally to the numerical value of a given property
Use "OGCObject>>#applyContinuousColorationOn:withFeatureData:withAssociateKey:withColor:" method, with following arguments:
apply continuous coloration on: the data key to use from your CSV
with feature data: your CSV as a parsed object (you can use NeoCSV Pharo package)
with associate key: the key which is common to feature properties and your CSV, used to join them
with color: the color to scale for display
This is an example with the number of cinema screens per metropolitan French region.
We applied especially here:
model applyContinuousColorationOn: 'nbEcrans' withFeatureData: csv withAssociateKey: 'code' withColor: 'blue'.
You can display it launching "GeoJSONExamples class>>#nbCinemaScreensPerFrenchRegion".
Continuous coloration based on the number of cinema screens per French region
In fact, the opacity of blue fill-color changes with the number of cinema screens per region "nbEcrans", given in following CSV (based on open data from data.gouv.fr) :
You can also display a continuous coloration per French region, based on the number of cinema entries ("GeoJSONExamples class>>#millionNumberOfEntriesPerFrenchRegion") or the average profit per entry in € ("GeoJSONExamples class>>#averageProfitPerEntryPerFrenchRegion").
Continuous coloration based on the number of cinema entries per French region
Continuous coloration based on the average profit per entry per French region
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