Monthly Archives: August 2008
We have been studying paragliding. We mapped the paraglider’s GPS track in ArcGIS Explorer, calculated the vertical and total distance traveled, measured its velocity, and then used a web resource to obtain the total distance in the horizontal and vertical dimensions. Now, let us consider an even more accurate measure of the distance traveled.
Because the Earth is an oblate spheroid, calculating a more accurate distance between two points requires spherical geometry and trigonometry. The Great Circle Distance Formula is one method, which uses double-precision (about 15 digits of accuracy) and the conversion of latitude and longitude values from decimal degrees to radians. Divide the latitude and longitude values by 180/pi, or 57.29577951. After conversion to radians, use:
3963.0 * arccos[sin(lat1) * sin(lat2) + cos(lat1) * cos(lat2) * cos(lon2 - lon1)]
If you do not first convert the latitude and longitude values in the database to radians, you must include the degrees-to-radians conversion in the calculation. Substituting degrees for radians, the formula becomes:
3963.0 * arccos[sin(lat1/57.2958) * sin(lat2/57.2958) + cos(lat1/57.2958) * cos(lat2/57.2958) * cos(lon2/57.2958 -lon1/57.2958)]
r * acos[sin(lat1) * sin(lat2) + cos(lat1) * cos(lat2) * cos(lon2 - lon1)]
Where r is the radius of the earth in whatever units you desire. r=3437.74677 (nautical miles)
r=3963.0 (statute miles)
If the software application or programming language you are using has no arccosine function, you can calculate the same result using the arctangent function, which most applications and languages do support:
3963.0 * arctan[sqrt(1-x^2)/x]
x = [sin(lat1/57.2958) * sin(lat2/57.2958)] + [cos(lat1/57.2958) * cos(lat2/57.2958) * cos(lon2/57.2958 - lon1/57.2958)]
Compare the result of this formula with the results that you obtained using the first manual calculation method and with the easier method on the web. How much do the three methods differ in meters? Which do you think is the most accurate? The length of the track is also stored in the GPS receiver. Do you think the track length stored in a recreational grade GPS is more accurate than your calculated values?
GIS and GPS can serve as excellent bridges between disciplines, in this case, mathematics, physics, and geography. What other phenomena could you map and analyze with these tools?
- Joseph Kerski, Education Manager
At the recent ESRI Education User Conference, some folks asked where to learn about using ArcExplorer Java Edition for Education (AEJEE), ESRI’s free, downloadable, dual platform (WinXP/MacOSX), lightweight GIS tool. With the traditional school year getting underway, this seems like a perfect time to mention these sources.
The best place to get started learning to use AEJEE is its on-board tutorial. Yup, built right into AEJEE is a 58-page PDF instruction booklet that walks you thru all the basics. After firing up AEJEE, click the “Help” menu and hit “Help Contents”.
The next great place to find instruction is within a brand new book from ESRI Press, Book#1 of the new “Our World GIS Education” series. “Thinking Spatially Using GIS” walks young students and technologically timid users thru some great exercises where they see the power of GIS while learning how to do things in AEJEE.
A number of excellent individual lessons await users at the ArcLessons website also. Choose “By Software – ArcExplorer” and see what strikes your fancy.
The final great way to learn new tricks in AEJEE is to browse the old entries in the EdCommunity Blog. Click the “AEJEE” tag option and scroll all the titles! Very easy!
- Charlie Fitzpatrick, ESRI Education Manager
The new ESRI Resource Centers provide content, web help, and support for users of serveral ESRI tools, including ArcGIS Desktop. Content for ArcGIS includes maps, layers, globes, and globe layers. Much of this content is provided by ArcGIS Online as free services. Including:
|World Street Map
|World Shaded Relief
|World Physical Map
We have been examining how one might study sports such as paragliding in 3-D using ArcGIS Explorer. We mapped the GPS track of the paraglider, and how to calculate vertical change and vertical velocity. Let us now calculate the total flight length.
As my ESRI colleague Matt took off from Alyeska Ski Resort, Alaska, above, he took his first coordinate. His last coordinate was collected upon his touchdown over an hour later. From his GPS track, select his first and last coordinate:
|Latitude, Longitude,||Date, Time,||Altitude(m)|
One can use simple math to roughly calculate the distance between two points in miles by the formula: sqrt(x * x + y * y)
where x = 69.1 * (lat2 – lat1)
and y = 53.0 * (lon2 – lon1)
Using the values for Matt’s flight:
X = 69.1 * (60.967984 – 61.041198) yields x = 5.059 miles
y = 53.0 * (149.119363 – 149.051793) yields y = 3.581 miles
The total distance is then: sqrt (5.059 * 5.059 + 3.581 * 3.581), which yields a distance of 6.198 miles, or 9.97471 kilometers.
An improved distance can be found by the same formula sqrt(x * x + y * y),
but where x = 69.1 * (lat2 – lat1)
and y = 69.1 * (lon2 – lon1) * cos(lat1/57.3)
Using these values yields 5.47406 miles, or 8.80964km of horizontal distance.
Paragliders move in the vertical dimension too, of course. Matt descended from 1802.609 meters to 50.12598 meters, or 1752.48302 meters total. Use the Pythagorean Theorem to determine the total distance that incorporates both the horizontal and vertical distances:
Total distance = sqrt ((8,809.64m * 8,809.64m) + (1752.48302m * 1752.48302m), which yields 8,982.25m or 8.98 km.
Remember that this total is straight line distance. Matt’s actual winding course down the valley can be calculated from importing the track into ArcMap, measuring it, and then applying the Pythagorean Theorem to account for the altitude lost.
Matt traveled 8.98 km in 1:21:32 (or, 1.359 hours), or 6.608 km/per hour, or 4.11 mph. One of the attractions of paragliding might be that one glides along at the pace of a brisk walk. However, in a paraglider, one must pay much more attention to what one is doing!
-Joseph Kerski, Education Manager.
The ArcGIS Explorer Team is pleased to announce that ArcGIS Explorer 500 was released just a few minutes ago.
This is an update release that includes:
- Support for ArcGIS Online subscription services.
- Proxy server support improvements.
- A change to allow installation on machines running Windows 2000.
The new ArcGIS Explorer 500 home server files will be available later this week. For those that deploy ArcGIS Explorer from your own home server, you’ll need to swap your versions and update your version.html file to push out the new release to your users.
I recently discussed how one might map and study a 3-D sport such as paragliding using ArcGIS Explorer. Mapping paths in the horizontal and vertical dimensions is just one of many interdisciplinary activities possible from paragliders or any other object from which you can obtain GPS tracks. Integrating mathematics and physics is easy through the analysis of the resulting coordinates and elevation values.
For example, examine the GPS track below from my ESRI colleague Matt as he began his flight at Alyeska Ski Resort near the Cook Inlet, Alaska (http://www.alyeskaresort.com).
|Latitude, Longitude||Date, time||Altitude(m)|
Have students calculate the rate at which Matt’s altitude rose during his launch: He rose 11.55 meters in 3 minutes and 21 seconds, at a rate of 3.44 meters per minute, or .057 meters per second.
Soon after, Matt rapidly lost altitude as he flew down the valley toward the Cook Inlet, as shown in the data below:
|Latitude, Longitude||Date, time||Altitude(m)|
Have your students calculate Matt’s descent: 51.911 meters in 38 seconds, or 1.366 meters per second. His descent was 24 times faster in the vertical dimension than his increase in altitude during takeoff. At this rate, I am sure that Matt felt the wind in his hair! Ask students to visualize these numbers by showing them a photograph of this part of the flight:
The numbers also make sense when one maps the data using ArcGIS Explorer:
Paragliding is only the beginning. Try mapping and analyzing other objects for which you can obtain horizontal and vertical data. Today, phenomena are tracked on, above, and even below the surface of our world as never before. For example, after analyzing the paragliding data that I have posted on ArcLessons, you might analyze whale migration data using WhaleNet (http://whale.wheelock.edu/Welcome.html).
In the next blog, I discuss how one can calculate Matt’s total distance traveled.
-Joseph Kerski, Education Manager.
- Right-click on the installer and choose Properties.
- In the Compatibility tab, check the box next to “Run this program in compatibility mode for” and select Windows XP using the pulldown menu. Click on OK.
- Double-click on the installer and use the installation wizard to install the program. When installation is complete, you will find AEJEE under All Programs > AEJEE.
- Luis F. Perez, M. Ed. Ph. D. Student in Instructional Technology, University of South Florida, College of Education
The 2008 ESRI UC promises to be the best to date, with this year’s theme, GIS: Geography in Action, a major focus of the first day’s activities. Featuring the latest innovations in ArcGIS 9.3, user successes, and a glimpse into the future of GIS, the Monday Plenary Session will provide you a rich learning experience.
ESRI President Jack Dangermond will host the day’s events, starting with a welcome and a chance to introduce yourself to fellow attendees. One of the highlights every year is when Jack acknowledges many examples of users’ work. Several user-focused awards, including the Making A Difference and President’s Award, will be presented.
After celebrating the accomplishments of GIS users, the session will focus on Jack’s vision for GIS in action. You’ll see the latest advancements in ArcGIS 9.3 that will help make you more productive including new capabilities for connecting ArcGIS Desktop and Server to the GeoWeb.
The afternoon session will look toward the future of GIS, our profession, and our planet. Jack will be joined by ESRI staff to give you an exclusive glimpse into the future of ArcGIS. They will showcase the newest GIS research and development using the ESRI software and solutions suite.
The always amazing K-12 Education special presentation will feature the application of geography and GIS by today’s youth. We’ll honor both students and educators doing terrific GIS work in the classroom.
This year’s keynote address will be given by renowned botanist, environmentalist, biodiversity expert, and director of the Missouri Botanical Garden, Dr. Peter Raven. Dr. Raven will discuss the significance of plant life and the environment in sustaining our world, as well as the threats ecosystems face today. Learn about the numerous threats, such as the destruction of natural habitats, over-consumption, and climate change, that are affecting biodiversity. Dr. Raven will also discuss how we can help preserve and improve our planet’s sustainability.
The first day of the conference wraps up with the Map Gallery Opening and Welcome Reception, where you can view a myriad of examples of GIS users making a difference using geography in action. The reception begins immediately following the Plenary Session.
Erin Brook, Roger Palmer, Anita Palmer, Kathryn Keranen, and Robert Kolvoord, authors of Our World GIS Education book series, and Anne Knowles, editor of Placing History: How Maps, Spatial Data, and GIS Are Changing Historical Scholarship
1:30 p.m. to 2:45 p.m. on Tuesday, August 5, in Room 30A of the SDCC – The panelists will discuss how GIS is used to develop spatial and analytical skills and foster a sense of involvement and better understanding of world events.
The 2008 ESRI Education Conference kicked off this morning with the plenary session, held at the Marriott Hotel adjacent to the San Diego Convention Center. The Education Team started the morning off, providing updates on K-12 and Higher Education, the Education Community website, and curriculum development and resources.
ESRI Technical Marketing then wowed attendees with the latest and greatest enhancements to ArcGIS 9.3 and ArcGIS Explorer. Productivity enhancements, bookmarks enhancements, resource center updates, HTML pop-up, and spatially enabled PDFs were demonstrated. These new technologies concluded by showing the new RSS capabilities of ArcGIS Explorer, including demonstrations for use with BioBlitz and recent earthquakes.
Angela Lee reviewed ArcGIS Online and the new ArcGIS Data Appliance. ArcGIS Image Server updates and its future inclusion with Higher Ed site licenses was announced. Improvements to AEJEE (relative paths, better color rendition) were reviewed. ArcLogistics, for efficient fleet routing, was introduced. ArcPad enhancements for mobile data collection and management were also highlighted.
Charlie Fry, manager of the ESRI Cartography Team, shared his inspiring historical investigation in the presentation “Citing and Using Historical Sources in GIS”. Using several primary sources, Charlie has created an amalgam of historical locations draped across a tapestry of historical base maps. Charlie’s historical study focused on using GIS to tell the story of Bunker Hill and much of the Revolutionary War from multiple perspectives.
Dr. Anne K. Knowles, Professor Geography at Middlebury College, capstoned the morning’s events as she explored the rich relationship between history and GIS – expanding on her expertise of historical scholarship and teaching history with GIS. She explored the use of GIS to investigate the Dust Bowl, Gettysburg, the Holocaust and other significant historical events.
This afternoon, attendees can visit the GIS EXPO and Hands-On Learning Center, attend concurrent sessions, and later in the evening, participate in the GeoTeasure Hunt!