Geocoded Photographs and GPS

Geocoded photographs are photographs that have a geographical location associated with them. This location can have a latitude, longitude, and altitude, or it can have a street address. Even a bearing can be included for the point position of the photographer for the direction the camera was pointing. Photographs can be automatically geocoded by using a connected GPS. A digital camera that supports GPS can provide the geocoding support. The GPS data is automatically stored in the photo's EXIF information when the photo is taken. A GPS receiver can be built into the camera or the camera can be connected by a cable to a separate receiver. A photograph taken without geographical information can be processed later providing an external GPS receiver produced the necessary GPS data. A timestamp from a clock in the camera that's synchronized with the clock of the GPS receiver are compared with the GPS receiver's timestamp giving resulting coordinates that can be be added to the EXIF information of the photo. Even if no GPS device was present when the photograph was taken, the geocoding information can be later added. The information can be manually entered by giving the coordinates or by selecting the location from a map. Some ways are less precise. The city, ZIP Code, or a street address can be entered. Even descriptive data of the location of the image can be entered. Specialized scene software such as Photosynth can recognize a landmark or photograph location by comparing to other photographs with known locations. Gecoded photographs can be uploaded to sites such as Flickr where the photograph is placed onto a map to view the location the photograph was taken. This can be useful for users who want to browse photographs from a map or search for photos from a given area to find related photographs of the same place that may have come from other users.

GIS Day 2007

In case anybody is interested in GIS in foreign countries such as ABTech was in Mexico. GIS Day was held in 83 countries in 2007 according to the GIS Day web-site. The countries are Afghanistan, Angola, Argentina, Australia, Austria, Azerbaijan, Bahamas, Bangladesh, Barbados, Belarus, Bolivia, Botswana, Brazil, Bulgaria, Burkina, Faso, Cameroon, Canada, Central African Republic, China, Colombia, Congo, The Democratic Republic of the Costa Rica, Croatia, Rep. of Czech Republic, Denmark, Egypt, Eritrea, Estonia, Ethiopia, Finland, France, Germany, Hong Kong, Hungary, India, Iran, Italy, Jamaica, Kenya, Latvia, Lebanon, Liberia, Lithuania, Malawi, Malaysia, Mexico, Mozambique, Nepal, Netherlands, New Zealand, Nigeria, Norway, Oman, Pakistan, Peru, Philippines, Poland, Portugal, Puerto Rico, Romania, Russia, Rwanda, Samoa, Saudi Arabia, Serbia, Slovak Republic, Somalia, South Africa, Spain, Sri Lanka, St. Helena, Sweden, Switzerland, Tanzania, Thailand, Trinidad & Tobago, Turkey, United Arab Emirates, United Kingdom, United States, Venezuela, Vietnam, and the Virgin Islands (British).

High Sensitivity GPS

High Sensitivity GPS receivers like Assisted GPS can be used in many cases indoors. Although High Sensitivity GPS can't be used in some indoor situations. Also, it doesn't instantly work when it's been off for too long of a period of time. High Sensitivity GPS does not require additional infrastructure. Large banks of correlators and digital signal processing are used to search for GPS signals very quickly. Therefore, High Sensitivity GPS receivers are very fast to first get a "fix" when the signals are at their normal levels such as being outdoors. Even when GPS signals are weak such as being in indoor situations, the extra processing power can be used to integrate weak signals so that position and timing can still be utilized. High Sensitivity GPS receivers are able to acquire signals up to 1,000 times weaker than conventional GPS receivers, and may be up to 30 dB more sensitive. High Sensitivity GPS receivers are able to track through 3 layers of dry bricks or up to 20 cm of steel reinforced concrete.

Assisted GPS

Assisted GPS is a type of GPS used in cell phones. It has advantages over many ordinary GPS units in that it can work in poor signal conditions that ordinary GPS doesn't work, such when there are obstructions such as tall buildings, trees, and being indoors. This make the cellphone useful for calling E911 in many cases where many ordinary GPS units could loose a signal. Another advantage is that with assisted GPS an Assistance Server is used. The Assistance Server locates the cell phone through what cell site on the cellular network it is connected to at the time. The Assistance Server has such good satellite signal and computation power that it can compare fragmentary signals relayed to it by cell phones, with the satellite signal it receives directly, thereby the cell phone's position is known. The Assistance Server can supply orbital data for the GPS satellites to the cell phone. Some ordinary GPS units may not get to download the almanac and ephemeris information until a clear signal is received continuously for up to one minute. Which means the GPS won't function if this information needs to be updated. Another advantage of using the Assistance Server is it can have better knowledge of ionospheric conditions and other errors affecting the GPS signal, thereby enabling more precise calculation of position. The accuracy of assisted GPS is between 5-10m. Perhaps the latest technology is even more precise. The assistance server can also offload most of the work of CPU and programming required for a GPS Phone.

zooming in on buidings

Not only does maps.live.com have the feature of seeing the aerial view close up of buildings, but Google Earth also has this feature, although a little different. Google Earth and, maps.live.com if you have the 3D turned on, has north and west coordinates in addition to the actual elevation in feet. I could see the elevation differences, assuming it's accurate, in different places of my property as the cursor, or hand, skimmed the area. Maps.live.com has a clearer picture, at least in 2D, in some areas I checked anyways. Both of them don't always put the address point at the actual property. Google Earth had many extra features such as the predicted high and low temperature of the day, points of interest, sometimes pictures of the area that you click to view, and other things. Google Earth seemed to "crash" sometimes. I think it was when I was panning or tilting the viewpoint sometimes.

geocoding exercise

Three typical approaches that have been used for CAD-GIS integration.

These three approaches of CAD-GIS integration I gleaned from www.esri.com.

File translation:
The conversion of data from one file format to another. This could be using an intermediate file such as ArcInfo Workstation in it's DWG-DXF-Coverage translator.
Direct read:
The data is read and converted on the fly into memory without an intermediate format.
Sharing access to a database:
Access to data on the fly is done by embedding an application program interface (API) on one system.