Analyzing Imagery and Change Over Time

Peter Becker and Vinay Viswambharan demonstrate how Dubai has changed in the last 40 years.

Jul 23rd, 2012

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00:01So let me tell you about my trip to Dubai last year.

00:03I was riding through the streets of Dubai and looking around and realizing, why are all these buildings so modern?

00:10So I turned to my friend Hossam and said, "Why are there no old buildings in Dubai?"

00:15And he said, "Well, the answer's simple: the United Arab Emirates is a country that's only 40 years old."

00:21The city, the country really is that modern.

00:25So that created the challenge and the question for our next presentation, which is to answer the question...

00:30...How much has Dubai changed in the last 40 years?

00:34To answer this, please welcome Peter Becker.

00:41Thanks, John. So let me show you.

00:42Here, a map of Dubai, with recent Landsat imagery.

00:49Let me zoom in to the old part of Dubai and change time back to 1975.

00:56Dubai, a small, coastal town, a single runway.

01:01By the year 1990, it had expanded, the town as well as the runway.

01:06By the year 2000, further expansion and more vegetation.

01:12Let's highlight that.

01:15We can see there's coastal development, and by the year 2000, they had built massive islands in the form of palm trees out into the gulf.

01:27By the year 2010, further development along the coast.

01:32But what if we want to actually measure this change?

01:35Well, I can use this tool to find an area of interest.

01:43And the system now computes the areas, returning for me that, in 1975, it was all barren land.

01:52By the year 2000, about 4 kilometers of urban growth; by 1942, over the year 2010, over 40 kilometers of urban growth.

02:03Vegetation had increased, and interestingly, the water area had actually gone down by about 12 kilometers...

02:10...due to the development of the palms.

02:13Now, what is the basis of this application?

02:17Well, there are three key things here - one, the world Landsat services...

02:22...two, the ability for ArcGIS Server to perform dynamic classification...

02:27...and the integration of these geoprocessing tools into a web application.

02:32So let me show this to you in ArcGIS Desktop 10.1, that many of you already have.

02:38Here, I can search online for Landsat imagery.

02:44This returns me the newly released Landsat services.

02:49They have been extended to include the new GLS 2010 data from the USGS... well as additional radiometric corrections and additional visually enhanced services.

03:00I can add these directly to ArcGIS Online, and they're available for you to use today.

03:08This service is a service that actually shows one of the capabilities of 10.1 to enable a single service to have multiple products.

03:16Here, I can pick the visualization analysis, and you will see the enhanced visual quality of these services.

03:26Let's zoom in to Dubai.

03:27The server performs the processing, returning me the required product.

03:32And from within Desktop, I can add additional enhancements, for example, add a dynamic range adjustment.

03:40As in the web application, we can use time and go back and have a look at what did Dubai look like in the year 2000?

03:49Or, move back forward to the year 2010.

03:55Now, although this is a seamless image service, I can actually get information about the actual pixel values... well as meta information about the individual scenes.

04:08Now, a new capability that we're adding in 10.1 is for ArcGIS Server to perform dynamic processing or dynamic classification.

04:19And to show this, I'm going to bring in this local server connection, and we'll see similar services based on the same imagery.

04:27If we now look at the products available, mind you, I can get to see, for example, this land/water interface...

04:37...or go and have a look at a full class land use.

04:43These same services I can then use in a geoprocessing tool.

04:47Here, I bring it up.

04:49It allows me to define the service's input, allows me to define an area of interest, and then, this will be processed.

05:03The tool is making multiple requests to that service.

05:06The server is dynamically calculating that classification, returning the classification results to the geoprocessing tool...

05:13...which then gets the statistics and generates the required reports.

05:19As soon as these are completed, they can be displayed.

05:22This same geoprocessing service is then shared with the web application to enable the dynamic reports.

05:30So I've shown how the extensive imaging capabilities within ArcGIS 10.1 can be used to measure the growth of Dubai...

05:39...but we know Dubai has also grown with a lot of tall buildings.

05:43And to show you how we can measure the vertical growth, let me introduce you to Vinay Viswambharan...

05:48...from the software development group.

05:51Thanks, Peter.

05:57So you just saw analysis and classification done at a city scale.

06:02I want to show you characterization of change at a finer level of detail.

06:06To do this, I need high-resolution imagery.

06:10So here's a WorldView scene over the area of Dubai.

06:14I receive this as raw, unprocessed TIFF files on disk.

06:17Now, one of the biggest improvements we've made in ArcGIS 10.1, the system leverages the metadata that's provided...

06:24...and it can define products automatically.

06:28So as I drag my pan-sharpened product into map, the system pan sharpens, orthorectifies...

06:35...and creates a visually good-looking product on the fly.

06:44The best is yet to come.

06:48So this is the Burj Khalifa, the tallest building in the world.

06:52It's an amazing structure, and that's some beautiful imagery to complement it.

06:57But that's obviously not the most intuitive view of the tallest building in the world.

07:02Using the sensor model information, we can now rotate my view and get a better perspective.

07:15Leveraging the sensor model information and using the meta information...

07:20...we've improved the analytical capabilities of ArcGIS even more.

07:24You can now make measurements off of your imagery.

07:28You can base it off the sensor geometry from the bottom of the structure to the top of the structure...

07:35...or you can make shadow base measurements from the tip of the shadow, tip of the spire, to the tip of the shadow.

07:46When characterizing change, you typically work with historical imagery.

07:51A common problem faced when working with historical imagery, your imagery doesn't line up.

07:58Let's navigate over to another place in Dubai.

08:03So here I have an older image.

08:05As you can see, the change is not quite obvious, but a problem with the image misalignment is a lot more obvious.

08:14These roads, they don't quite line up.

08:18ArcGIS 10.1 can fix this.

08:21We have this magic button.

08:24No, seriously, you'll like this.

08:27I'll bring up the Georeferencing toolbar, I'll hit it, and I'll tell you what it does.

08:32You're going to like this.

08:33The system is computing tie points between the two images.

08:37It's adjusting the images to fit automatically.

08:41Now, this is great for the historical imagery that I'm dealing with.

08:44And like I told you, it's a very simple workflow.

08:47Press a button, pick your images, no tie points, no control points, no check points.

08:52There is no complexity the user needs to deal with.

08:57Just like that, it fits.

09:08You can now compare the two images, automatic georeferencing.

09:14We can now navigate back over to the Burj, compare the two images, lines up perfectly.

09:21For five years, that is a lot of change.

09:25But if you notice, most of the change, much of the change is tall buildings, a lot of vertical growth.

09:32Vertical growth equates to massive change in floor area.

09:37Now, to compute change in floor area, or to quantify change, you need to measure building heights.

09:47So as I zoom out to the extent of Dubai, you can see that's a lot of data collection that I have to do...

09:52...and a larger collection of images to deal with.

09:55So here's where the mosaic dataset comes in.

10:00Now that's a lot of imagery.

10:03It's processed on the fly, and it's fast.

10:11As I zoom out to the extent of the Middle East, 2,500 scenes, GeoEye scenes, two and a half terabytes of imagery.

10:24It's processed on the fly.

10:33I've shown you all of this functionality.

10:36I've shown it to you in Desktop.

10:38But ArcGIS, it's a system, which means we can wrap all of this functionality into a rich, focused web application...

10:46...and I can crowdsource my data collection task to a larger group of people.

10:53So here's my web application.

10:56I've hosted it on my organizational account on ArcGIS Online.

11:01As I bring it up, the application lets me measure building heights and other attributes.

11:07And just like in Desktop, from the tip of the building to the tip of the shadow, I can attribute my building.

11:17Image services, like all of ArcGIS, are time aware, which means I can actually step through these images in time...

11:28...and you can see, the structure was first observed in 2009.

11:35On the right-hand tab, I have my reports populated; I have other statistics as well.

11:43So to answer John's question. How much has Dubai changed over the years?

11:48The city has changed a lot.

11:52With 96 percent of buildings captured by my organization, the approximate increase in the total floor area - 190 square kilometers.

12:03But John, why just numbers?

12:06Using these measurements, I can actually show you what it looks like.

12:13So here's the beautiful city of Dubai at night.

Copyright 2016 Esri
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