Posts Tagged ‘accuracy’

The Accuracy and Precision Revolution: What’s ahead for GIS? (Nighbert via ArcUser)

Wednesday, April 7th, 2010

acc_precis_5-lg

[Editor's note: "As we try to integrate highly resolved data into existing GIS, the errors in legacy data will become more apparent." Jeff outlines the problem through his experience at the BLM in Oregon. Jeff is also responsible for early "bump mapping" of digital terrain models (DEMs).]

Republished from the ESRI ArcUser Winter 2010.
By Jeffery S. Nighbert, U.S. Bureau of Land Management

The ability to obtain precise information is nothing new. With great patience and skill, mapmakers and land surveyors have long been able to create information with an impressive level of accuracy. However, today the ability to determine and view locations with submeter accuracy is now in the hands of millions of people. Commonly available high-resolution digital terrain and aerial imagery, coupled with GPS-enabled handheld devices, powerful computers, and Web technology, is changing the quality, utility, and expectations of GIS to serve society on a grand scale. This accuracy and precision revolution has raised the bar for GIS quite high. This pervasive capability will be the driver for the next iteration of GIS and the professionals who operate them.

When I say there is a “revolution” going on in GIS, I am referring to the change in the fundamental accuracy and precision kernel of commonly used geographic data brought about by new technologies previously mentioned. For many ArcGIS users, this kernel used to be about 10 meters or 40 feet at a scale of 1:24,000. With today’s technologies (and those in the future), GIS will be using data with 1-meter and submeter accuracy and precision. There are probably GIS departments—in a large city or metro area—where this standard is already in place. However, this level of detail is far from the case in natural resource management agencies such as Bureau of Land Management (BLM) or the United States Forest Service. But as lidar, GPS, and high-resolution imagery begin to proliferate standard sources for “ground” locations, GIS professionals will begin to feel the consequences in three areas: data quality, analytic methods, and hardware and software.

Continue reading at ArcUser . . .

Comparison of Touch Screen Sensor Accuracy (Apple Insider)

Friday, January 22nd, 2010

diytouchscreenanalysis3

[Editor's note: This graphic reminds me of lens distortion matrix analysis in my remote sensing class back in university. Not all sensors are made equal and pictures and sensors just capture a representation of reality, not the real thing.]

Republished from AppleInsider. January 11, 2010.

Touchscreen analysis shows iPhone accuracy lead over Droid

A test comparing the accuracy and sensitivity of smartphone touchscreens across various makers gave the iPhone top marks ahead of HTC’s Droid Eris and the Google-branded Nexus One, and much better results than the Motorola Droid.

The results, published by MOTO labs, noted that the company (which has no relation to Motorola) “has years of experience developing products that use capacitive touch, and we’ve had the opportunity to test many of the latest devices. Our conclusion: All touchscreens are not created not equal.”

Continue reading at AppleInsider . . .

Being the Fastest Is Not Enough (InfoGraphicsNews)

Wednesday, August 19th, 2009

mapita22

[Editor's note: You'll start seeing more mashups on The Washington Post site the next month. Staff are being trained to use a new mashup maker tool I made that churns out decent maps in 5 minutes flat. Just like in print, normal rules about accuracy in reporting apply. The bottom line, don't show more location detail than you know to be true, as this blog post from InfoGraphicsNews illustrates. Thanks Laris!]

Republished from the InfoGraphicsNews blog.
Original on 12/04/2008.

Yesterday, the terrosrist group ETA killed another person in Spain. In this cases, as most of the cases, internet media have the initative. The first idea is to place the new. Shw where it took place. But the problem is that in this kind of news all the information is changing all the time during the first hour, and the data are not accurate. Yesterday, we only knew that Ignacio Uria was killed while he was going to his favourite restaurant, Kiruri. We didn’t even knew if he came form his house or form his job.

The punch line:

None of those that placed the killing on a exact place were right.

Some rectified later, others didn’t even change it. Being the fastest can’t go before telling the truth. On reconstructions many editors use to say that “the reader know this is not exactly the truth, that we’re just guessing”. I don’t want the reader to not trust us. I prefer to have a reader who really think that when we say something we know it and we’re not guessing.
These are screenshots from some spanish websites two hours after the agencies gave the news:

Continue to view screenshots at InfoGraphicsNews blog . . .

Privacy and GeoTagging Photos with GPS-enabled iPhone

Tuesday, July 29th, 2008

flickr geotag example map

Being able to record where a photo is taken one of the key features of the new iPhone. Not only does the phone capture a great picture but there is no residual “Now where was I”. You can instantly see where the photo was taken on a detailed map. This is great for geocoding when surveying, but what are the social implications?

Do you want to share this level of detailed personal information?

Why wouldn’t you? Consider this:

Upload a week’s worth of photos.

  • One taken on the way into work of that cute gal you always see at your metro station
  • Another in your office for a coworker’s going away party
  • Another taken at your favorite dance club
  • Another taken at the great brunch place you go to on Saturdays and
  • Another of the pile of laundry you’ve been ignoring all week

Normally you are adding captions and keywords that someone who already knows you can piece together and perhaps guess or already knows where all these physical places are. But you’ve gate-keeped based on “you need to know me and know enough about me” to get it.

Up until now, you’ve controlled the information flow based on how much you tag the photo in the context of how well your online “friends” know you.

Related links: adding GPS locations to photos when you don’t have a GPS (one) (two) (three) (four) (five).

GPS tagged photos are game changing

Now someone who doesn’t know anything about you, and with whom you might NOT want to share that level of personal information, can instantly become your first stalker. They know exactly where you live, exactly where you work, exactly how you get to work, and exactly where you relax and have let down your guard.

Something to consider as an adult and perhaps lock-down if your child has a GPS-enabled cell phone.

Of course, if you’re on a tourist trip and taking pictures of Yellowstone and the Statue of Liberty and are never going to be there again it’s perfectly fine to include the full GPS coordinates since that doesn’t disclose personal information and you’ll not routinely passing by there again. However, if you visit Aunt Mildred in Brooklyn on the same trip you might want to limit access to her home’s location.

I’m invincible, right? What do I care?

Consider the following two situations:

  • I was at a friend’s house party on Friday and took a few pictures and was about to post them when it hit me: I’m potentially compromising her safety, not just my own. If I post those GPS enabled photos some random person could view the photo (hey, it’s up on Flickr for anyone to browse) and know which front door to be waiting at. Skechadellic, dude!
  • I have a swimming hole I’d like to keep on the down-low but when I go out there I take a few shots with my camera to remember the scene. If I post those on Flickr with the GPS coordinates suddenly anyone that views my the photo tagged “My secret swimming hole” can see it placed exactly on that blue map polygon and route directly to it. Not so secret after all. Oops!

So it turns out Flickr has a way to moderate this to an extent. There is a setting to control this, sort of. Screenshot below:

flickr geotags

Notice how I do NOT have this option checked. But my GPS information is still being read in and placed on my account map somehow. Bad!

User Solution 1

The best, fail-proof option is to not record the GPS information when the photo was taken. But then you loose that information for your personal record. The iPhone asks the first time a GPS enabled application is launched if you want to allow it access to the GPS. Press “Don’t Allow” and you’re set.

But once you have enabled the camera to know the location you can’t disable it until the phone is turned completely off and restarted, less than convenient and oh so easy to forget about. You can go to the General Settings area of the phone and turn Location Service on and off without restarting the phone, however.

iphone use current location

User Solution 2

There should be a middle way when uploading and displaying on photo sharing sites like Flickr. This way you retrain full GPS location for your private records but only let out an approximate public location for everyone else.

For the Mac you can download PhotoInfoEditor to edit the precision of the GPS coordinates stored in the EXIF information for the photo (or a duplicate targeted for public upload). I had a devil of a time finding this app as most simply report the GPS coordinates; they do not allow them to be edited. If someone knows of a comparable app on the PC please email me.

Notice in the screenshot below that I have stripped the latitude and longitude to display to the hundredth (39.35° N). You could just as well scramble the coordinates down to the 4th or 5th decimal position when in the city and still be in the right neighborhood but no longer be at the right building. Photosets can be batched adjusted.

This puts the photo in the rough vicinity of the actual location but does not reveal the actual location

. photo info editor screenshot

When you do this before uploading to Flickr or Picasa you can have the benefit of placing your photos on a map with some accuracy but just not with a high precision. In other words, don’t zoom too far into the map or the photo locations become inaccurate. But zoomed out they are perfectly acceptable.

How can software be improved?

On upload / display of the photos in a social photo site:

  • Group permissions for viewing Placename tags and GPS coordinates on map with default being NOT to show the geographic location but to apply limits of precision with individual photo exceptions as detailed next:
  • On / off toggle for Placename tags per photo
  • On / off toggle for GPS coordinates per photo
  • Placename precision (country, state, county, town, neighborhood) from Yahoo or Google geocoder as a slider control per photo
  • GPS precision (exact, 1/4 mile, 1/2 mile, 1 mile, 2 mile, 5 miles, 10 miles, 20 miles, 60 miles) for latitude and longitude as a slider per photo

The GPS precision needs to take into consideration that the number of earth miles at each degree of latitude changes. Simply chopping of decimal places is a crude solution. A more elegant solution would be to add a random ± X decimal degrees to the actual location at the target precision. Even though the iPhone GPS can get you down to 10 meter accuracy, sometimes you don’t want to be that precise.

I’ve already spoken to the developer at AirMe which is my favorite app on the iPhone for uploading to Flickr and he seems interested in making the required upgrades to his application. Please help spread the word to other developers!