Geospatial File Formats

Last updated on 2026-10-17 | Edit this page

Estimated time: 45 minutes

Overview

Questions

  • What are the common file formats for vector and raster data?
  • What are the limitations of the shapefile?
  • Which format should I use to work with, to share, and to archive my data?

Objectives

  • Recognize the most common vector and raster file formats and their file extensions
  • Explain the strengths and limitations of shapefiles, GeoPackages and GeoJSON
  • Distinguish open from proprietary formats
  • Choose a suitable format for working, sharing and long-term storage

Why formats matter

The same map layer can be stored in many file formats. The choice affects whether others can open your data, whether attribute names and values survive, how large the files are, and whether the data will still be readable in twenty years. A few questions to ask of any format:

  • Is it open (a published, freely implementable specification) or proprietary (controlled by one company)?
  • Is it one file or several that must stay together?
  • Does it preserve the coordinate reference system, field names, data types and null values?
  • How large can it get, and how fast is it?

Vector formats

Format Extension(s) Open? Notes
Shapefile .shp .shx .dbf .prj (and others) Published by Esri The old standard; widely supported but limited (see below)
GeoPackage .gpkg Yes (OGC standard) One file holding many vector layers, tables and even rasters; the default in QGIS
GeoJSON .geojson Yes (IETF RFC 7946) Plain text; ideal for the web and small datasets; always in longitude and latitude (WGS 84)
KML / KMZ .kml .kmz Yes (OGC standard) Google Earth’s format; good for sharing with the public, weak for analysis
CSV with coordinates .csv Yes A table with x and y (or longitude and latitude) columns; only points; the CRS must be documented separately
File geodatabase .gdb (a folder) No (Esri) ArcGIS’s main format; readable by QGIS and GDAL, but best kept for ArcGIS workflows
GeoParquet .parquet Yes (open specification, version 1.1) Columnar format for large datasets and cloud analysis; growing quickly

The trouble with shapefiles

The shapefile dates from the early 1990s. It is everywhere, and every GIS can read it, but it has real limitations:

  • Several files make one dataset. At minimum .shp (geometry), .shx (index) and .dbf (attributes); usually also .prj (coordinate system) and .cpg (text encoding). Lose the .prj and the layer no longer knows where it is; lose the .dbf and the attributes are gone.
  • Field names are limited to 10 characters. produce_available becomes produce_av, and two long names can collide.
  • Text fields hold at most 254 characters, and there is no true date-and-time type.
  • Each file is limited to 2 GB.
  • One geometry type per file, and no way to store several layers together.
  • Null values are poorly supported, so missing numbers often turn into 0.

None of these are a problem for a quick download, but they cause silent data loss when you save your own carefully designed data as a shapefile.

Callout

Prefer GeoPackage for your own work

A GeoPackage is a single file (an SQLite database) that can hold all the layers of a project, with long field names, real date and time fields, proper null values and no 2 GB limit. It is an Open Geospatial Consortium (OGC) standard and the default format in QGIS. If you receive shapefiles, it is good practice to convert them to a GeoPackage at the start of a project.

Raster formats

Format Extension(s) Notes
GeoTIFF .tif .tiff The standard raster format: a TIFF image with georeferencing built in; supports many bands and data types
Cloud Optimized GeoTIFF (COG) .tif A GeoTIFF organized so programs can read just the part they need over the web; an OGC standard
JPEG 2000 .jp2 Compressed imagery; used by Sentinel-2
NetCDF and HDF5 .nc .h5 Multidimensional arrays (for example, temperature by latitude, longitude, height and time); common for climate and Earth observation data
Zarr a folder A cloud-friendly format for very large multidimensional arrays
ASCII grid .asc A plain-text grid; easy to read, but large and slow
PNG or JPEG with a world file .png + .pgw An ordinary image plus a small text file of georeferencing; fine for display, not for analysis

Compression

Raster files can be compressed to save space. Lossless compression (such as DEFLATE or LZW in a GeoTIFF) keeps every value exactly. Lossy compression (such as JPEG) discards detail to save more space, which is acceptable for a background image but not for data you will measure or analyze.

Tables

Tables without geometry are often the largest part of a social science project. CSV is the safest format for sharing them: it is plain text, opens anywhere, and will remain readable for decades. Spreadsheet files (.xlsx) are convenient for editing but can hide problems: merged cells, formulas, colors that carry meaning, and automatic conversion of codes such as 01001 into the number 1001 or of MAR1 into a date.

Callout

Watch out for leading zeros

FIPS codes and GEOIDs often start with zero (01 is Alabama, 01001 is Autauga County). Opening a CSV in a spreadsheet program can silently turn them into numbers and drop the zero, breaking every later join. Import ID columns as text, and check them after every conversion.

Which format when?

Purpose Good choices Why
Working copy of a project GeoPackage (vector), GeoTIFF (raster) Complete, fast, few limitations
Sharing with collaborators GeoPackage, or the format they use One file is easy to send
Web maps and small datasets GeoJSON Readable by web libraries and by people
Very large vector data GeoParquet Fast, compact, cloud-friendly
Large imagery shared online Cloud Optimized GeoTIFF Readers can fetch only what they need
Long-term preservation Open, well-documented formats: GeoPackage, GeoJSON, GeoTIFF, CSV Readable without any one company’s software

Converting between formats

Conversions are routine (in QGIS, right-click a layer and choose Export > Save Features As…), but each one is a chance to lose information. After converting, check:

  • that the coordinate reference system is still correct
  • that field names were not shortened and data types did not change (text IDs becoming numbers)
  • that null values did not become 0 or empty strings
  • that the number of features is the same
  • that special characters (accents, non-Latin scripts) display correctly

Behind most GIS software, including QGIS, is the open-source GDAL library, which reads and writes more than 200 formats. That is why QGIS can open almost anything you are given.

Challenge

What went wrong?

A colleague sends you a zip file containing stores.shp and stores.dbf. When you open it in QGIS, the points appear near the coast of Africa, and a field called produce_av holds values that should be in produce_available. What happened, and what would you ask for?

The .prj file is missing, so QGIS does not know the layer’s coordinate reference system. The points are probably in a projected system (with coordinates in meters) being read as degrees, or in degrees being read as the wrong system, so they land near 0° latitude, 0° longitude. The .shx index is also missing, which some software cannot do without. The shortened field name is the shapefile’s 10-character limit. Ask for the complete set of files (including .shx and .prj), or better, a GeoPackage, plus the CRS (for example its EPSG code).

Challenge

Choose a format

What format would you use for each, and why?

  1. A field team’s grocery store points, with long field names and a date and time for each visit
  2. A small layer of 20 campus buildings for an interactive web map
  3. A 40 GB set of Landsat images to share with collaborators who will analyze small areas
  4. A table of ACS estimates by census tract that will be archived with a thesis
  1. GeoPackage: long field names, true date and time fields and proper nulls; a shapefile would truncate names and lose the times.
  2. GeoJSON: small, plain text, and read directly by web mapping libraries.
  3. Cloud Optimized GeoTIFF: collaborators can read only the areas they need instead of downloading 40 GB.
  4. CSV, with GEOIDs stored as text and a data dictionary describing each column: open, simple and durable.
Key Points
  • Formats differ in openness, number of files, size limits and what attribute information they preserve
  • Shapefiles are universal but limited: several files, 10-character field names, 2 GB, weak null support
  • GeoPackage is a good default for your own vector work; GeoTIFF for rasters; CSV for tables
  • Prefer open, well-documented formats for sharing and preservation
  • Check the CRS, field names, data types, nulls and feature counts after every conversion