HOTOSM Tools¶
Data Types¶
There are two main types of geospatial data we must consider for maps.
Raster¶
This is imagery data - a picture (jpeg, png, tiff, etc).
On the lowest level the data is represented by pixels.
The pixels are assigned a value within a band:
- Single band: the image could be greyscale, where the pixel value contains a level of gray on a spectrum from white-black.
- Multi band: most images encountered in the OSM world will contain three bands (RGB), which can be imagined to be stacked on top of one another. Red, green, and blue are primary colours than when combined can form any other colour.
We are mostly interested in multi-band optical imagery, i.e. what you may see on Google / Bing Satellite.
This underpins the usage of other data, by visually locating it in space - it tells you where your data is!
Vector¶
This is point, polygon, and line data - what you find on OSM!
The shapes are represented by some complex maths underneath and rendered on your screen.
This is the data that is typically layered on top of basemaps (either raster or vector-based basemaps) for usage.
How is this data used?¶
Input Data¶
- Raster Basemaps:
- Google, Bing, ESRI, Mapbox et al all provide web basemaps we can use.
- Open Aerial Map (OAM) provides more bespoke basemaps of particular areas of interest (AOIs), over a certain time period. Often higher resolution.
- Vector Data:
- OpenStreeMap (OSM) is the biggest reference of open map data.
- HOT's Export Tool & Raw Data API provide easy access to this.
- Any other vector data in various formats:
- GIS layers provided by governments: region boundaries, roads, etc.
- Data collected by NGOs and other organizations, open or not.
- OpenStreeMap (OSM) is the biggest reference of open map data.
All of this data can be used for various purposes, involving processing and data analysis.
Processed Data¶
Generally always vector data in our context.
It's OSM vector data that has been processed and packaged in a certain way so it can be used by other tools / users.
Using the input data described above, we want to produce data with additional value:
- To generate new data to feed back into OSM (a complete loop).
- For other purposes such as humanitarian response, data analysis and reporting.
HOT's Tools¶
With the above as context, HOT's tools roughly can be categorised as such:
Input¶
| Tool | Description |
|---|---|
| OAM | Get base imagery. |
| Raw Data API | Extract data from OSM easily for software. |
| Underpass (OSM) | Assure data quality. |
Note: input may be into our own tools, or workflows of others.
Each tool is fully open to use by the public.
Output¶
| Tool | Description |
|---|---|
| TM | Digitize map features remotely. |
| fAIr | Speed up the remote digitization process |
| FMTM | Add extra information to digitised features in the field. |
| Export Tool | Extract data from OSM easily for humans. |
OpenAerialMap (OAM)¶
OAM should underpin all of our tools.
Integrations into other tools allow for basemaps to be loaded to better inform mapping.
The thing with satellite imagery is that you have lots of different resolutions available, through different providers.
You need to use a mix of providers and decide on the best quality usable for mapping.
Many providers (ESRI, Bing, etc) provide free base maps we can use, but OAM should be more targeted - the highest resolution imagery we can get over a time period of interest, for a specific AOI that may be used in TM or FMTM.
Raw Data API & Underpass¶
They use an innovative database structure to make OSM data much more usable. The idea to make OSM data more accessible, searchable / filterable, and create extracts in formats that can be consumed either by software or users.
Underpass is a quality control tool that will sit on top of Raw Data API.
Export Tool¶
The purpose of Export Tool is to:
- Take the users input for what data they need, over what area.
- Calls Raw Data API to extract and filter the data.
- Receives back the data in the user requested format, e.g. a JSON for use in another tool, or a geopackage for use in GIS software by a user.
Tasking Manager¶
Creating additional vector data to go into OSM, using raster imagery as a source.
Pretty much creating polygons and lines from things you and see on a map and uploading them to OSM.
The mapping is crowdsourced, or organised by NGOs.
Resulting data needs to be validated.
Another tool, MapSwipe, can help with this & may be part of the solution. However, TM allows mapping to be done collaboratively.
fAIr¶
TM is labour intensive. fAIr uses localised training data to generate a model that can be used to predict vector features from a raster image.
Integration into TM means mapping of features can be a lot faster.
FMTM¶
Adding useful tags, in the field, from the vector data created in TM.
The tags provide extra information about what features actually are in OSM.
Again, the mapping can be crowdsourced, but more likely organised by NGOs / govs.
The FMTM mapping could also provide a feedback loop to TM, helping to validate that features were mapped correctly.
As with TM, another tool, StreeComplete, can help with this & may be part of the solution.
However, FMTM allows mapping to be done collaboratively.