Skip to content
Kharita Challenges

Problems

Real geospatial problems, graded automatically. Choose a track, a level and what you want to hand in.

20 of 59 problems

Pick one for me
Track
Spatial Analysis10 problemsPostGIS / SQL1 problemPython5 problemsRemote Sensing5 problemsCartography7 problemsWeb GIS6 problemsData Management10 problemsGIS Architecture3 problems
Level
Beginner3 problemsIntermediate9 problemsAdvanced8 problemsExpert0 problems
Hand in
SQL14 problemsPython14 problemsGeoJSON15 problemsAnswers20 problemsSchema1 problemDecisions2 problemsDataset file5 problems
Category
Data preparation1 problemData quality4 problemsSpatial analysis0 problemsRaster analysis3 problemsCartography3 problemsDecision support3 problemsGeospatial systems0 problemsWeb delivery6 problems
Sign in to track progress
AnswersClear all
  1. Not started, How many tiles does an offline London need?Web deliveryAnswers

    From a bounding box to a tile count: size the offline basemap for a field app across zoom 10–15.

    Web GISbeginnerDifficulty: beginner140 XP~25 min3 checks

    You hand in your answers as values.

    Dataset

    • London boroughs · Polygon · 33 features · EPSG:4326

    What you’ll do

    • Take the bounding box of the borough layer
    • Convert box corners to tile coordinates at each zoom
    • Count tiles per zoom and total them into a storage estimate
    XYZ tilesWeb Mercatorofflinecapacity planningLondonAlso trains Cartography
    Open problem
  2. Not started, What is Greater London made of?Raster analysisAnswers

    A class histogram on a 10 m land-cover raster: the shares a planning document quotes, and the reason a pixel count is not quite an area.

    Remote SensingbeginnerDifficulty: beginner140 XP~25 min5 checks

    You hand in your answers as values.

    Dataset

    • Greater London land cover 2021 (ESA WorldCover 10 m) · Raster · EPSG:4326

    What you’ll do

    • Read a categorical raster and count pixels per class
    • Express classes as shares of the valid pixels
    • State what the number is and is not
    land coverWorldCoverhistogramrasterLondonAlso trains Data Management
    Open problem
  3. Not started, Which airport codes will break the schedule join?Data qualityAnswers

    Audit a registry's identifiers before they become a join key: missing, malformed and duplicated codes, and positions that are only approximate.

    Data ManagementbeginnerDifficulty: beginner130 XP~25 min5 checks

    You hand in your answers as values.

    Dataset

    • World airports · Point · 893 features · EPSG:4326

    What you’ll do

    • Find nulls, duplicates and malformed values in an identifier column
    • Distinguish a key defect from a position defect
    • Report counts the integration can be sized against
    data qualityidentifiersjoin keysaviationAlso trains Python
    Open problem
  4. Not started, Accept the rasters, or send them backData qualityAnswers

    The checks a data manager runs on delivered rasters before anyone analyses them: extent, nodata, value range, and whether the figures are plausible for the place.

    Data ManagementintermediateDifficulty: intermediate200 XP~35 min6 checks

    You hand in your answers as values.

    Datasets

    • Greater London elevation (Copernicus DEM GLO-30) · Raster · EPSG:4326
    • Greater London land cover 2021 (ESA WorldCover 10 m) · Raster · EPSG:4326
    • Greater London, Sentinel-2 red and NIR, 11 July 2025 · Raster · EPSG:32630

    What you’ll do

    • Read raster metadata and full-resolution statistics
    • Distinguish nodata from valid extremes
    • Record facts a later dispute can start from
    raster QAnodatametadataacceptanceLondonAlso trains Remote Sensing
    Open problem
  5. Not started, At which zoom does every capital get its own tile?Web deliveryAnswers

    Count capitals per XYZ tile across zooms to decide where a label layer switches from clustering to one label per city.

    Web GISintermediateDifficulty: intermediate180 XP~25 min4 checks

    You hand in your answers as values.

    Dataset

    • Populated places · Point · 1,251 features · EPSG:4326

    What you’ll do

    • Convert points to tile indices at several zooms
    • Find the busiest tile per zoom
    • Choose a switch-over zoom from the data
    XYZ tileslabelsclusteringzoom levelsglobalAlso trains Cartography
    Open problem
  6. Not started, At which zoom does the dock layer fit in a tile?Web deliveryAnswers

    Count features per XYZ tile across zoom levels to set a vector-tile pipeline's minimum zoom and its per-tile limit honestly.

    Web GISintermediateDifficulty: intermediate190 XP~30 min4 checks

    You hand in your answers as values.

    Dataset

    • Santander Cycles docking stations (live snapshot) · Point · 799 features · EPSG:4326

    What you’ll do

    • Convert coordinates to tile indices at several zooms
    • Count features per tile and find the maximum
    • Choose a minimum zoom from the data rather than a default
    vector tilesXYZtippecanoezoom levelsLondonAlso trains Spatial Analysis
    Open problem
  7. Not started, How big does Web Mercator make Greenland?CartographyAnswers

    Put a number on the most famous distortion in cartography: the same countries measured on the ellipsoid and on the projection every web map uses.

    CartographyintermediateDifficulty: intermediate210 XP~30 min4 checks

    You hand in your answers as values.

    Dataset

    • Countries · MultiPolygon · 241 features · EPSG:4326

    What you’ll do

    • Measure area geodesically or in an equal-area projection
    • Project the same polygons to Web Mercator and take their planar area
    • Express the distortion as ratios a reader can repeat
    Web Mercatorprojectionarea distortionEqual EarthglobalAlso trains Spatial Analysis
    Open problem
  8. Not started, How green was London on 11 July 2025?Raster analysisAnswers

    Compute NDVI from a two-band Sentinel-2 clip, handle nodata and integer types properly, and report the distribution a monitoring programme quotes.

    Remote SensingintermediateDifficulty: intermediate220 XP~35 min4 checks

    You hand in your answers as values.

    Dataset

    • Greater London, Sentinel-2 red and NIR, 11 July 2025 · Raster · EPSG:32630

    What you’ll do

    • Compute a band ratio index with correct types
    • Exclude nodata from every statistic
    • Summarise the index as the programme's three figures
    NDVISentinel-2band mathnodataLondon
    Open problem
  9. Not started, The buffer that shrank on the way to the mapCartographyAnswers

    Quantify what a 400 m buffer drawn in EPSG:3857 actually covers on the ground in London, and how much of the coverage report it loses.

    CartographyintermediateDifficulty: intermediate200 XP~30 min4 checks

    You hand in your answers as values.

    Datasets

    • Santander Cycles docking stations (live snapshot) · Point · 799 features · EPSG:4326
    • London boroughs · Polygon · 33 features · EPSG:4326

    What you’ll do

    • Derive the Web Mercator scale factor at London's latitude
    • Translate a projected buffer distance into its ground equivalent
    • Re-run the coverage analysis with the shrunken buffer and measure the shortfall
    Web Mercatorscale factorprojectionbufferLondonAlso trains Spatial Analysis
    Open problem
  10. Not started, When the attributes and the geometry disagreeData qualityAnswers

    A reference gazetteer carries a latitude and a longitude column beside its geometry. Audit how far apart they are, and what else does not add up.

    Data ManagementintermediateDifficulty: intermediate200 XP~35 min5 checks

    You hand in your answers as values.

    Dataset

    • Populated places · Point · 1,251 features · EPSG:4326

    What you’ll do

    • Compare each feature's geometry to the coordinate attributes it carries
    • Count the disagreements at two thresholds and identify the worst
    • Find keys the downstream spreadsheet cannot distinguish
    data qualitygazetteerhaversineduplicatesglobalAlso trains Python
    Open problem
  11. Not started, Which ports in the registry are the same port?Data qualityAnswers

    Find probable duplicates in a facility registry by combining a name match with a distance rule — and separate them from the honest homonyms.

    Data ManagementintermediateDifficulty: intermediate190 XP~30 min4 checks

    You hand in your answers as values.

    Dataset

    • Ports · Point · 1,081 features · EPSG:4326

    What you’ll do

    • Find repeated identifiers in a registry
    • Combine an attribute match with a spatial rule to separate duplicates from homonyms
    • Size the missing attribute that would resolve the rest
    data qualitydeduplicationhaversineregistryglobalAlso trains Spatial Analysis
    Open problem
  12. Not started, Why a cloud-optimised GeoTIFF is cheap to serveWeb deliveryAnswers

    Read a COG's internal structure — tiles, overviews, bytes — and turn it into the numbers a tile server's capacity plan rests on.

    GIS ArchitectureintermediateDifficulty: intermediate200 XP~30 min4 checks

    You hand in your answers as values.

    Datasets

    • Greater London land cover 2021 (ESA WorldCover 10 m) · Raster · EPSG:4326
    • Greater London, Sentinel-2 red and NIR, 11 July 2025 · Raster · EPSG:32630

    What you’ll do

    • Read a GeoTIFF's block size and overview structure
    • Count internal tiles from dimensions and block size
    • Relate the structure to what a tile request costs
    COGGeoTIFFtile servercapacity planningrasterAlso trains Web GIS
    Open problem
Show 8 more problems

12 of 20 problems shown