- What is OS Surface 1?
OS Surface 1 is a one-metre resolution Digital Surface Model (DSM) of Great Britain, representing an elevation model of the earth's surface. It includes all permanent and non-permanent features including buildings, rocks and vegetation.
OS Surface 1 is derived from our aerial photography, the same source data we use to update our OS MasterMap Topography Layer and Imagery Layer, making it synchronous with our other OS products.
- What are the benefits of using OS Surface 1?
OS Surface 1 comprises data that covers England, Scotland and Wales and currently provides approximately 88% coverage of Great Britain. It is captured within our three-year flying programme which ensures the currency and coverage of the data.
A one-metre resolution provides superior accuracy for remote data interrogation in uses such as flood modelling, line of sight analysis and vegetation management. This cuts costs by reducing the need for time-consuming site visits.
- How often will OS Surface 1 be updated?
Update frequency will be dependent on customer feedback. Blocks of Digital Surface Model (DSM) data are produced in order of currency set within our three-year update schedule.
- How is this data supplied?
OS Surface 1 is published as 1km2 uncompressed GeoTIFF tiles. The georeferencing in a GeoTIFF is embedded in the imagery file itself.
Unlike a standard TIFF file, a GeoTIFF does not require an associated TIFF World File (TFW) to geographically position the data. OS Surface 1 data is supplied as a full set of Great Britain tiles and is available as download only. The national dataset is supplied as 1km2 tiles of data within a 5km2 folder.
- How is the accuracy of the product measured?
OS Surface 1 is based on a capture and update methodology that involves no editing of data. It is derived from our aerial photography by a process of pixel matching and image based pixel correlation. Ground control points are used in the data to measure against observed values from surveyed ground measurements.
- What is RMSE?
RMSE - or Root Mean Square Error - is a statistical measure of accuracy that compares the likely error between two datasets comparing a predicted value and an observed value.
All RMSE (z) results are represented using a Confidence Level of 95%. This is the level of certainty with which you will estimate the true population value. Confidence levels state the probability that the value of a parameter falls within a specified range of values. A 95% confidence interval is a range of values that you can be 95% certain contains the true mean value of the population.
- Where can I find metadata for OS Surface 1?
Metadata such as latest flying date exists for each tile of data, and you can find this as a CSV file.
- Where can I see the coverage extent for OS Surface 1?
The following coverage extent shapefile for OS Surface 1 can be downloaded from the product support page. You can see the areas covered in our shapefile (zip).
- What licence do I need to evaluate OS Surface 1?
If you are an OS Partner, you will need to accept two of our licences in OS Orders - our Developer Contract Licence and our Data Exploration Licence (DEL). We’ve done this to enable Partners to access the data quicker for the six-week evaluation period.
You can download sample data from our OS Surface 1 product page.
If you're an existing customer, you can log in to OS Orders to download a larger area of sample data. By downloading the sample data, you agree to being contacted by OS for feedback.