How to Find Reliable GIS Data You Can Trust
- Claire Birnie
- Jul 15
- 5 min read
One of the biggest misconceptions in ecology I come across is the notion that finding reliable GIS data is hard.
If that’s what you think, you might want to look away now: I disagree.
What is hard, however, is knowing whether the data you've found is actually any good.
I've lost count of how many times I've opened a project and found someone using outdated datasets, missing information or mapping that isn’t detailed enough for what they’re trying to achieve.
So, why does this happen?
Well, when you're an ecologist, GIS is usually just one part of your job. You've got surveys to complete, reports to write and looming deadlines.
Spending hours investigating data quality?
Nah, it’s probably not at the top of your list, mate.
But it’s still important and you don't need to become a GIS specialist to make better decisions about the data you use.
How to make sure your GIS data is usable
To make sure you don’t waste time gathering data you don’t need, heed this advice:
1. Start with the end goal
Before downloading any data, ask yourself this question:
What am I trying to produce?
Your answer will influence the type of data you need.
If you're creating a location map for a report, your requirements will differ from those of someone mapping polygons for a Biodiversity Net Gain assessment.
I know that's obvious when you say it out loud, but it's surprising how often people start gathering data before they've fully thought about what the final output needs to look like.
Why waste time on stuff you don’t need?
2. Bigger isn't always better (oo-er!)
Another massive misconception is that the most detailed dataset must be the best one.
Sometimes that's true, but a lot of the time you’re giving yourself more work.
The important thing is making sure the scale and resolution match the task.
For example, if you're digitising habitat boundaries around a development site, you'll need a higher level of detail than if you're producing a county-wide overview map.
I've also seen the opposite happen. Someone uses a small-scale (left image) dataset because it's quick to download, then wonders why the boundaries don't line up with aerial imagery or survey results.
The dataset wasn't necessarily wrong; it just wasn’t designed for that purpose.
So, always check:
What scale was the data created for?
How detailed is it?
Is the level of detail suitable for the decisions you're making?
A reliable dataset used incorrectly will produce unreliable results.
3. Metadata isn't exciting, but it’s useful
Nobody gets excited about metadata, but spending two minutes looking at it will save you loads of time later.
Metadata tells you things like:
Who created the dataset
When it was collected
When it was last updated
The coordinate reference system
Any known limitations
Licensing information
If you're working on a planning project and discover halfway through that your dataset is six years out of date and the most recent was last week, that's not a conversation anyone wants to have.
A quick metadata check at the start helps you avoid surprises later.
4. Give the data a sense check
Before you rush blindly into your work, have a look at what you've downloaded:
Does it look sensible?
Do the features line up with the contextual mapping you’re using?
Are there obvious gaps?
Do the attributes contain the information you'd expect?
Sometimes the quickest quality control check is simply zooming in and having a good mooch around.
If something feels off, investigate it before carrying on.
5. Don't forget to check the geometry
This is one of the most useful habits you can develop when working with GIS data.
Geometry checking helps identify issues like:
Overlapping polygons
Small gaps between features
Duplicate geometries
Self-intersecting polygons
Invalid shapes
These errors aren't always obvious when you're viewing the map, but they can be a massive pain in the arse later when you're calculating areas, running analysis or producing outputs for clients.
Most GIS software includes tools to automatically identify and repair geometry issues, so it's worth building this into your workflow, especially if you're working with habitat mapping, BNG calculations, or survey boundaries.
So, where do I get reliable GIS data?
There are lots of data sources available online, but these are some of the places I regularly point clients to:
Ordnance Survey OpenData
This should be your first call for basemapping and contextual information.
Depending on your project, products such as Open Zoomstack, OpenMap Local and VectorMap District can provide useful background mapping.
DEFRA Data Services Platform
This is one of my favourite resources. Here, you'll find datasets including:
LiDAR
Terrain models
Surface models
Aerial photography
Environmental data
If you're working in the environmental sector, it's well worth bookmarking.
National Data Library
Here you’ll find a huge catalogue of datasets from government departments, local authorities and public bodies.
It's often my first stop when I'm trying to track down a specific dataset.
NatureScot
A cracking wee website that’s a valuable source of environmental and ecological data for projects in Scotland.
Natural Resources Wales
Got a project in Wales?
No problem, Natural Resources Wales is another useful resource where you'll find environmental datasets and mapping information.
Your actual clients!
I can’t tell you how many people overlook asking their clients, but ask them and you’ll find they have lots of valuable data you can look at, including:
Previous survey information
Existing GIS layers
Aerial imagery
Licensed Ordnance Survey data
Always ask what they have available before spending time searching elsewhere.
Good GIS data starts with reliable data
You don't need every dataset available or a complicated workflow. And you definitely don't need to spend days downloading information you'll never use.
What you do need is data that's suitable for your project, from a source you trust and have checked before you start working with it.
Get this right and your maps and analysis will improve, saving time on problems later.
Which, if you're anything like the ecologists I work with, means more time getting your actual job done
Woop!
Need help getting your GIS workflows sorted?
Whether you're new to GIS or looking to improve the way you or your team works, I offer QGIS training designed specifically for ecologists and environmental consultants.
From sourcing reliable GIS data to creating efficient workflows in QGIS, my courses are built around the way environmental professionals actually work.
Catch ya next time,
Claire
PS. Check out my article, Should I hire an external GIS training provider? , if you're deciding whether to learn GIS yourself, train your team in-house or bring in specialist support.
