3D satellite photo showing some of the 775 ground survey points

PhotoSat publishes 21 new satellite surveying accuracy studies

3D satellite photo showing some of the 775 ground survey points

3D WorldView-2 satellite photo of Asmara, Eritrea, showing some of the 775 ground survey points that determine the 14cm PhotoSat surveying accuracy.

21 PhotoSat surveying accuracy studies from seven different stereo satellites

PhotoSat has published 21 new satellite surveying and mapping accuracy studies, now available on our website. The studies include data from seven different stereo satellite systems. The best results show elevation surveying accuracies of better than 15cm.

The accuracy studies include stereo satellite data from the following satellites:

  • WorldView-1
  • WorldView-2
  • WorldView-3
  • Pleiades-1B
  • KOMPSAT-3A
  • SPOT-7
  • ALOS PRISM

 

PhotoSat has measured accuracy on over 750 stereo satellite surveying projects

PhotoSat has delivered over 750 satellite surveying projects since 2007 and we have carried out accuracy evaluations on the majority of them. Most of the survey data on these projects belongs to our customers and cannot be shared publically; however, customers have provided feedback on many of these projects.

The results of these 21 new accuracy studies are consistent with our project accuracy evaluations and customer feedback.

 

PhotoSat accuracy test areas in Eritrea and California

The accuracy studies were conducted over two test areas. One test area is west of Asmara, Eritrea where PhotoSat has access to more than 45,000 ground survey points over a 50km by 20km block.

The second area is in SE California where PhotoSat uses a very accurate Opentopography.org open source LiDAR survey.

 

The effect of different numbers of ground survey points

The studies employed different numbers of ground survey control points for each test area and each satellite system. For some of the satellite stereo pairs the accuracy is significantly improved by increasing the number of ground survey control points.

For example, the WorldView-2 survey for Eritrea is accurate to 19cm in elevation with two ground control survey points, and accurate to 14cm in elevation with 21 ground control points.

In contrast, the accuracy of the WorldView-3 survey for the California test area is not improved by additional ground survey points. This WorldView-3 survey is accurate to 13cm in elevation with one ground survey control point and with 153 ground survey control points.

 

PhotoSat has been continuously producing satellite accuracy studies since 2007

In order to provide objective quantifiable accuracy data for stereo satellite surveying and mapping, PhotoSat has been continuously producing accuracy studies since 2007. We have previously published nine of these studies. The rest of the studies were used for calibrating and improving our processes.

 

21 new accuracy studies all processed with the same version of the PhotoSat processing system

The 21 new accuracy studies were produced with the most recent version (2016) of the PhotoSat processing system. Where possible we used satellite data produced by the 2015 or 2016 versions of the satellite operators’ ground processing systems.

 

Summary of PhotoSat 2016 accuracy study results

Satellite Test area km² GCP RMSE
WorldView-3 California 150 1 13cm
WorldView-3 California 146 153 13cm
WorldView-3 Eritrea 100 21 15cm
WorldView-2 California 173 1 15cm
WorldView-2 California 173 153 12cm
WorldView-2 Eritrea 100 21 14cm
WorldView-1 California 174 153 14cm
WorldView-3 Eritrea 198 2 19cm
WorldView-2 Eritrea 400 2 19cm
WorldView-1 Eritrea 100 21 19cm
WorldView-1 California 174 1 23cm
WorldView-1 Eritrea 420 9 23cm
Kompsat-3A California 144 14 21cm
Pleiades-1B Eritrea 189 74 26cm
Pleiades-1B Eritrea 189 1 28cm
Kompsat-3A California 144 1 50cm
Kompsat-3A Eritrea 130 11 48cm
Kompsat-3A Eritrea 130 1 53cm
SPOT 7 Eritrea 1,458 1 4m
ALOS PRISM Eritrea 2,300 3 2m
ALOS PRISM Eritrea 2,300 1 4m

See PhotoSat’s accuracy studies overview for full details.

For more information about PhotSat’s surveying accuracy, please see our satellite surveying case histories or visit the following links.

Satellite surveying

Measure Twice, Cut Once: The Importance of Satellite Surveying in Mine Site Planning and Construction

Oil sands elevation map with 50cm contours

Tailings elevation map with 50cm contours

Keeping a mine safe, profitable and compliant with legislation means frequent, accurate surveying. Planning begins with exploration and identification of likely sites, and particularly in oil and gas projects this can result in delays and false starts. Traditional methods of identifying potential sites suffer from major shortfalls, including the challenges of surveying large areas with traditional methods. The gap between geologists’ opinions and test drilling with a high likelihood of success has never been adequately filled, resulting in continuing requirements for multiple overlapping exploration techniques including exploratory drilling and ground-based surveying.

Mine site planning and construction has surveying needs that no other project matches. Like any engineering project mine site construction requires accurate surveying, but few other large engineering projects are built in hostile, difficult to reach terrain. And few others change so much or so fast. The fundamental fact about a mine is that it is dynamic – it alters the landscape and has to change itself too. That’s true of deep underground mining, open cast, leach mining and every other kind of mine operation.

Surveying Challenges

This presents surveying challenges. Mine sites are typically more remote than other engineering sites: the typical engineering project expands or connects to some built environment, while mines are usually in isolated places far from cities and infrastructure, meaning that they often require their own infrastructure. They’re often in rugged terrain too, or in climatic conditions that make surveying more difficult, such as the mountains of Argentina, the Australian outback, or the Arctic.

All of this means that mine surveying often can’t be done well with traditional tools. Even using modern on-the-ground tools like LiDAR and GPS, survey teams still need to travel to inhospitable terrain and map the site in weather that can range from uncomfortable to downright dangerous.

Then there’s the issue of changes to the mine site. While many of these occur underground in tunnel mines, even these produce significant amounts of waste rock. And larger open pit mines produce both overburden and (usually) tailings which must be monitored. Neither GPS nor LiDAR is usually fast enough to provide mine operators with monthly updates that allow monitoring and ongoing tailings planning and control. This is going to become a bigger issue over the next couple of years, post-Brazil.

So what about drones? Drone technology is in its infancy, so it’s likely to improve. Camera-carrying, real-time streaming drones are available to consumers for almost pocket-money prices; professional models can fly for hours and provide images of remote areas without risking human operators. Surely they can offer a solution?

Drones can do that. But they’re dependent on weather: just as much as larger aircraft, they can’t fly in high winds or see through clouds. They also require an on-site operator. Drones can do things a survey team can’t, like overflying tailings ponds, and they’re increasingly being offered as a solution to a mining industry that has more need for accurate, timely surveying than ever before – and less spare cash than before to spend on it. But they can’t provide the consistency and climate resistance that some mines require.

So far we’ve talked about surveying itself: gathering data. But the majority of data gathered, whether by ground or airborne LiDAR, GPS, drone overfly, or any other method, is just that: data, not information. Translating it into 3D models that resemble what’s happening on the ground and tells observers something they didn’t already know is a time-consuming, computer power-eating process. The acquisition and processing speeds, taken together, simply don’t match up to the pace of decision making that modern mining requires.

Satellite Surveying to the Rescue

All, that is, apart from satellite mapping. Satellites are unaffected by remoteness and inhospitable terrain. They’re definitely out of danger; whole mine sites can be imaged from space in one shot, including those areas where it would simply be impossible to send a survey team. And the accuracy of PhotoSat’s satellite elevation data is unparallelled: we deliver 30cm accuracy for mine site mapping, for instance.

More telling yet is the availability of the information. In contrast to processing times measured in weeks, PhotoSat uses a proprietary technology based on seismic survey data processing tools to drastically cut the time between data acquisition and final deliverables. For example, we map one of Suncor’s mine sites biweekly and deliver within just five days in order to meet their planning meeting deadlines.

PhotoSat’s proprietary image processing tech can be adapted to specific client needs too. For instance, our contract with Suncor involves using a mixture of high and low resolution elevation grids, depending on where the imagery is used and taken. We use high resolution data to map Suncor’s mature fine tailings pond, overburden dump, and mine pit advance to an accuracy of 15cm elevation or more. One result of this approach is that the same images can be used by multiple departments – PhotoSat derived images are passed along to Suncor’s Tailings Engineers, Geotechs and Production Planning departments.

Well sites in Alberta

Well sites in Alberta

During an unrelated project for producing SAGD well sites in Alberta, PhotoSat was able to identify 70 well sites, resulting in a total project cost of $12,000 – just $170 per well – during a project that lasted from initiation on January 30, 2015 through image acquisition on February 4th to processing completion on February 6, 2015. The accuracy of the well head locations we provided were within 11cm RMSE, as compared to Government of Alberta certified RTK surveying. We were able to provide 50cm contours and a 1m elevation grid over potential well pad areas without needing exploratory drilling, and without a single boot on the ground or drone in the air.

To learn more about PhotoSat’s revolutionary satellite topography system and what it can do for your business, contact us at info@photosat.ca or 604-681-9770.

Reconciling Inconsistent Survey Datasets

We often hear from our clients that one of their biggest challenges with existing survey data is the lack of consistency between datasets. On oil and gas projects there is often hundreds of thousands of dollars invested in survey data that the engineers have little confidence in. The Drilling, Completions, and Facilities Engineers often find mismatches and different accuracies amongst location datasets.

The type of survey data in question comes in many forms – from GPS, theodolite surveys, as-built location drawings, and other surface location data. With so many data sources, it’s not surprising that there are inconsistencies and therefore frustrations for the project engineers.

What all people working on the project need is one reliable dataset as a base. We have worked with oil and gas companies to develop a system for matching surface engineering datasets to our high accuracy elevation surveys and precision satellite photos.

PhotoSat then provides a reliable and coherent package of surface location data including a 1m elevation grid (DEM), accurate to within 20cm vertically. This engineering quality satellite survey data can then be used by the engineers for all future project work.

Mismatched survey datasets

 

Other benefits of having high accuracy satellite survey data:

  • Reduce ground crews needed for surface scouting and site surveying, which reduces costs.
  • Streamline well pad selection and engineering projects for facilities.
  • Accurate cut and fill volume estimates.
  • Use the data for other applications like pipeline and access road route planning, and seismic survey planning.

 

How does reconciling survey data work?

First we produce our 20cm accuracy elevation mapping package from high resolution stereo satellite photos.

The data package includes:

  • 1m bare earth elevation grid accurate to 20cm
  • 1m (or 50cm) contours
  • 50cm precision satellite photo

Then we figure out the relative match between the mismatched engineering datasets that you provide, and our detailed satellite survey. When we determine the data inconsistencies, we work with your team to choose a reference dataset and shift the other datasets horizontally and vertically to match to it. Our system typically results in the final datasets all matching to within 10cm vertically and 25cm horizontally.

In the end we provide you with your original survey engineering data, but now adjusted and verified and therefore reliable. You also receive our elevation mapping package as described above, and usually within about 8 days of the satellite photo collection. Clients then have a coherent suite of surface location data that can be used for future engineering tasks on the project. Our clients tell us having this trust in the data is very valuable, making decisions easier and shortening project timelines.

We completed a case study on reconciling surface data that you can view here for a detailed example.

If you’d like more information on this product or our other mapping services, feel free to contact us at info@photosat.ca or 604-681-9770.

Tailings dyke elevation image number 2.

Monitoring Tailings Dykes with Satellite Elevation Data

In both the oil sands and mining industries, the integrity of tailings dykes is extremely important. Recent tailings incidents demonstrate this. Mapping the tailings dykes and beaches can be challenging with hazardous conditions restricting access for ground surveyors. Using satellite-based elevation mapping allows for data to be collected remotely, with no risk for ground personnel and no permits needed. Regular topographic mapping during construction allows the design engineers to confirm that the dykes are being built to design specifications.

Currently PhotoSat regularly surveys the topography of tailings dykes for the Alberta oil sands mines to an accuracy of 15cm in elevation. In fact, we map the entire tailings systems for Suncor’s Millennium and Steepbank mines about every two weeks. These surveys are used by a wide range of engineers and planners at Suncor. They even did a presentation about their experience comparing different survey options and why they settled on PhotoSat’s technology as their main topographic survey method.

Tailings dyke elevation image

Elevation image of a tailings dyke, December. Red is high, blue is low.

Tailings dyke elevation image number 2.

Elevation image of the same tailings dyke 6 months later. Red is high, blue is low.

Unique Methods for Elevation Mapping

Satellites can collect imagery anywhere in the world, and with new high resolution satellites being launched regularly, there are more options and collection times keep getting faster. Also, PhotoSat has a unique, automatic system for processing stereo satellite imagery to extract the bare-earth elevation values. That’s right – we invented this process ourselves here in Vancouver, and continuously improve the system to get better and better accuracy results. Additional information about the technology we use can be found on the Technology page. And we test our system regularly by publishing accuracy studies that are available on our website here.

We also survey all parts of tailings projects beyond the dykes for a complete profile of a mine site tailings area, including the sand dumps, tailings beaches, and mature fine tailings. The advantage of satellites is that they can collect imagery over a large area in one shot, providing an instantaneous snapshot of the entire tailings beach waterline, the geometry of the beaches, and the height of the tailings dykes. Areas from 100-200 sq km can be collected in one satellite pass.

Our standard elevation accuracy specs for mining projects is better than 30cm, and you can find out more about our digital elevation data package here. If even higher accuracy is required, contact us as we often can provide higher accuracies depending on the project.

To find out more about our engineering grade satellite topography, contact us at info@photosat.ca or 1-604-681-9770.

Texas elevation data

High Accuracy Elevation Grids (DEM) Available for Texas Oil Regions: Permian Basin, Eagle Ford Shale

PhotoSat has produced off-the-shelf digital elevation models for parts of the Permian Basin and Eagle Ford Shale in Texas. For oil producing areas in Texas that are outside of the immediately available data shown below, we can quickly produce a DEM using existing satellite imagery so contact us (info@photosat.ca) with your project area and we will provide details.

The vertical accuracy of the 1m elevation grids is better than 1m, making the data suitable for engineering and precision GIS tasks. The terrain data is bare earth (DTM) with man-made features and vegetation removed, making it ideal for development and construction planning. These DEMs are used by our oil and gas clients for:

  • Reducing costs by lowering the need for ground surveyors and eliminating multiple surveyors.
  • Well site and well pad design
  • Pipeline route, powerline, and road planning
  • Seismic planning
  • Slope analysis
  • Environmental assessment and planning

Our Texas digital elevation models are offered at an affordable price for such high accuracy and high resolution. Contact us with your project area in Texas and we will provide you with a quote.

Below are images of the current coverage available. If your project area is outside of this coverage, don’t fret, we can quickly produce detailed topography over most other areas.

Texas elevation data

Overview of off-the-shelf elevation data in Texas

 

Permian Basin DEM

Zoom of the DEM in the Permian Basin

 

Eagle Ford Shale DEM

Zoom of the DEM in the Eagle Ford Shale Play

 

The elevation mapping package includes:

  • 1m bare earth elevation grid (DTM) accurate to better than 1m
  • 50cm greyscale precision satellite ortho photo
  • 1m contours

 

Eagle Ford elevation mapping

1m colour image of the DTM over the Eagle Ford Shale

 

1m contours

1m colour image of the DTM with 1m contours

 

Satellite photo

50cm resolution satellite ortho photo

 

If you’d like a quote for topographic mapping over your project area contact us and we’d be happy to help. info@photosat.ca, 604-681-9770.

Mexico onshore oil and gas blocks

High Accuracy Surveying and Satellite Photos for Mexico Round 1 Onshore Blocks

As you probably already know, Mexico’s oil and gas blocks are up for auction and the next round includes the onshore fields. For bidding companies, detailed satellite elevation mapping and high resolution ortho photos can significantly help understand and assess the surface topography.

View the brochure for Mexico blocks satellite data (PDF).

Mexico onshore oil and gas blocks

Mexico onshore oil and gas blocks for bidding

 

PhotoSat can provide 30cm vertical accuracy, 1m bare earth elevation grids (DEM) for all blocks. These DEMs are produced from archive satellite images.

The benefits of having high accuracy surveying include:

  • Assessing environmental conditions including drainage and flood risk assessment.
  • Engineering grade accuracy allows for accurate assessments of the location of existing infrastructure (well sites, roads, pipelines etc).
  • Knowledge of the ground conditions reduces risk.

If the available satellite images used to produce the topographic data are too old for your purposes, we can acquire new satellite images on request. Contact us at info@photosat.ca for information on the data available over the block in question, and for pricing.

We can accommodate custom coordinate systems and are able to use many types of surveys for ground reference points. We can also produce the mapping without ground control points if nothing is available. More information on our 30cm accuracy satellite elevation mapping can be found on our main website.

If detailed base mapping is not required yet, we can also provide high resolution satellite ortho photos only over the desired block.

The following table outlines the existing 50cm resolution satellite images that are immediately available for all blocks. Included are the size of the block and the most recent ortho photo date. If you need more current information, we can task a satellite to collect new images.

Campos Burgos:
Block Size (sqkm) Archive ortho image date
Anahuac 30 October 2014
Duna 37 March 2014
Mareografo 30 March 2014
Calibrador 16 March 2014
San Bernardo 29 November 2013
Benavides 136 November 2013
Pena Blanca 26 June 2015
Carretas 90 November 2013
Ricos 24 August 2013
Campos Norte:
Block Size (sqkm) Archive ortho image date
La Laja 10 July 2014
Ponton 12 August 2015
Paso de Oro 23 October 2014
Tecolutla 7 January 2014
Barcodon 11 March 2015
Campos Sur:
Block Size (sqkm) Archive ortho image date
Moloacan 47 June 2015
Calicanto 11 May 2015
Cuichapa Pte 42 June 2015
Mayacaste 22 April 2015
Tajon 28 April 2015
Paraiso 17 April 2015
Fortuna Nacional 22 June 2015
Mundo Nuevo 28 May 2015
Topen 26 May 2015
Catedral 58 May 2015
Malva 22 May 2015
Secadero 10 May 2015

 

Our standard delivery is an ortho photo centered on each block covering 100 sq km. Pricing is based on the square kilometer, and custom sizes and shapes are available on request.

View the brochure for Mexico blocks satellite data (PDF).

Feel free to contact us for a quote, or for any questions: info@photosat.ca, 604-681-9770.

 

Reconciling Surface Engineering Data

One of the biggest complaints we hear from our oil and gas clients is about inconsistent survey data. On the one hand, they’re spending thousands of dollars on surface engineering data, and the cost is justified because of its business value. That data saves money down the line. Except it doesn’t. Because when drilling, completions and facilities engineers get the data, they often can’t trust it.

It’s data that comes from GPS and theodolite surveys, as-built drawings, and from other sources that aren’t always even identified. Any given data point could have come from any of these sources. Frequently the engineering data is not reliable enough.

What’s needed is a data set that comes from one, reliable source. Then existing data sets can be compared against that. Instead of several differing views, there’s one authoritative, reconciled picture of what’s happening on the ground.

PhotoSat offers our oil and gas clients coherent project location data with elevation accuracies better than 20cm. Completions, facilities and drilling engineers can work from a reliable data set now and in future project stages.

Survey data sets for engineering projects

The value of surface engineering data is directly proportional to accuracy. We help our clients maximize the value of their engineering data by providing reliable data across the project site. That data can be used to inform cut and fill volume estimates as well as to streamline facilities engineering projects and well pad selection.

Additionally, surveying via satellite means less boots on the ground. Fewer survey teams have to work in hazardous working environments and less expensive equipment is exposed to the risk of damage at the project site. Data is also available in a usable form far more quickly, typically within five days.

So how does it work?

We start with the data set our client already has. Then we compare it against our own topographic survey. When we find inconsistencies, we work with the client’s project team to select the appropriate reference data set for that inconsistency, and shift the others horizontally and vertically to match it. This process usually means we’re leaving our clients with datasets that match to within 10cm vertically and 25cm horizontally. Clients also get a matching 1m grid of our satellite engineering topography, accurate to 20cm in elevation, and a 50cm precision satellite ortho photo with 25cm horizontal accuracy. That provides a reliable basis for future data-dependent engineering projects like surface design work, including cut and fill volume estimates.

We’ve delivered over 500 projects like this to clients all over the globe, and our clients know that there’s no better, faster or more accurate way to base their engineering data on something reliable and accurate. If you’d like to read more about how our data reconciliation process works, take a look at this engineering data case study. To find out how we can help you with your project, contact us at  info@photosat.ca or call us at 1-604-681-9770.

Accelerate Mining Volume Measurements with Satellite Topography

Accurate mine planning requires continually adjusting the plans for the situation on – and underneath – the ground. Resource quantities and locations are changing frequently, and mine layout is affected by blasting, tunneling and ore removal. That’s especially true in open pit mines, but all mining engineers face the difficulty of working with the same digital elevation data while the ground shifts.

In fact, that’s one problem that more efficient communication between the mine face and site and the engineer simply can’t solve, because no one on the ground has a high-level overview either. What’s needed is an update of the original elevation data to reflect what’s happened since.

A common method of doing this is with LiDAR (Light Detection and Ranging). But LiDAR is expensive and time consuming, so we need a mapping system that can be used more often. The only snag is that it has to both deliver similar accuracy and cost significantly less to permit more frequent use.

Step forward satellite topography.

Satellite topography using new, geophysical processing techniques results in similar accuracies to LiDAR and can be used for yearly, quarterly or monthly reconciliations, allowing engineers to work with accurate representations of what’s really happening on the ground. PhotoSat’s satellite elevation mapping for mining volumes has proven accuracies of better than 30cm, providing a clearer picture.

Mining volume changes over an open pit

Volume changes over an open pit mine

 

That means that when it’s time to make volumetric change measurements in pits, stockpiles, waste dumps and tailings, satellite mapping lets you view and analyze the situation simply and easily. Our clients tell us that one of the main advantages of using our satellite system is the ease with which they can check on as-built locations of buildings and structures and reconcile them to the original plan. Reconciliation can even be on a biweekly basis if the project is moving fast. That helps engineers with tailings management, and also makes life easier and safer for on-the-ground surveyors, resulting in greater accuracy and fewer injuries.

How can a satellite system deliver biweekly updates? Partly because after ground-based scans have been acquired, the images have to be compiled. In the case of a system like vehicle-mounted ILRIS (Intelligent Laser Ranging and Imaging) that’s the bottleneck; from raw data to point cloud to the computer processing and satellite location necessary to produce a useable image, nothing much can compete with the 8 days PhotoSat’s technology can take to produce a useable result.

Satellite image with mining volumes

Satellite photo with mining volume changes

 

Finally, using satellites rather than ground-based methods removes the need for surveying to take place on or near the mine site. As a result, the surveying process is safe and never needs to interfere with mine operations. There’s no risk of damage to vehicles or injury to surveying personnel when your imaging is done from space!

To find out more about how satellite topographic mapping can help make mining a safer and more efficient process, leave us a comment or contact us at info@photosat.ca.

LiDAR and satellite elevation data

PhotoSat verifies accuracy of DigitalGlobe’s 30cm WorldView-3 satellite elevation data to within 15cm

PhotoSat has recently completed a study to measure the accuracy of the elevation grid produced from the new 30cm resolution WorldView-3 (WV3) satellite. We measured the accuracy of our topographic mapping by comparing it to a highly accurate LiDAR elevation grid. The study was carried out over an 88 km2 area in Southeast California that overlaps an Open Topography LiDAR survey.

Read the full elevation accuracy report here (PDF)

For the study, PhotoSat produced a 50cm grid of elevations using our proprietary geophysical processing technology with stereo satellite images taken by WV3. Our resulting elevations were then compared to a 50cm LiDAR elevation grid, which is accurate to about 5cm. The resulting 15cm RMSE elevation accuracy was impressively achieved using a single ground reference point.

Below are some images of the elevation surveys and the differences between the datasets. You can also view the full WorldView-3 elevation accuracy study (PDF) on our website.

For more information on our highly accurate satellite topography, contact us at info@photosat.ca or 1-604-681-9770.

WV3 30cm resolution satellite ortho photo
Figure 1: WV3 30cm resolution satellite ortho photo created from WV3 stereo photos, for the area of the LiDAR survey used in this study.

LiDAR elevation grid
Figure 2: An image showing a portion of the LiDAR elevation grid. Lower elevations are blue, and higher elevations are red.

PhotoSat’s WV3 elevation grid image
Figure 3: PhotoSat’s WV3 elevation grid image covering the area of the LiDAR image. The grid has an elevation point every 50cm. At this scale, the LiDAR and WV3 images are identical. Lower elevations are blue, and higher elevations are red.

PhotoSat’s WV3 elevation grid clipped to the LiDAR extents
Figure 4: PhotoSat’s WV3 elevation grid clipped to the LiDAR extents, for areas with slopes less than 20% grade. Areas where development occurred since the 2008 LiDAR survey were removed for the accuracy analysis.

Differences between our WV3 elevation grid and the LiDAR elevation grid
Figure 5: The differences between our WV3 elevation grid and the LiDAR elevation grid, for areas with slopes less than 20% grade, are shown in a standard histogram on the left and a cumulative histogram on the right. If we assume that the LiDAR is perfect, the WV3 elevations have a Root Mean Square Error (RMSE) of 15cm. Ninety percent of the WV3 elevations are within 22cm of the LiDAR elevations giving a 90% Linear Error (LE90) of 22cm.

Comparison of the LiDAR and WV3 elevation grids for 1000m wide area
Figure 6: Comparison of the LiDAR and WV3 elevation grids for 1000m wide area. Minor differences between the elevation grids are visible at this scale.

Continue reading PhotoSat verifies accuracy of DigitalGlobe’s 30cm WorldView-3 satellite elevation data to within 15cm