The Global Positioning System (GPS) is a network of about 30 satellites orbiting the Earth at an altitude of 20,000 km. The system was originally developed by the US government for military navigation but now anyone with a GPS device, be it a SatNav, mobile phone or handheld GPS unit, can receive the radio signals that the satellites broadcast.
Wherever you are on the planet, at least four GPS satellites are ‘visible’ at any time. Each one transmits information about its position and the current time at regular intervals. These signals, travelling at the speed of light, are intercepted by your GPS receiver, which calculates how far away each satellite is based on how long it took for the messages to arrive.
"Local folklore has it that the tree grew when George Washington planted his walking stick while he and the Continental Army were encamped in nearby Newburgh during the final years of the Revolutionary War but core samples of the tree have dated its growth to 1699, well before American independence. Franklin Roosevelt often came to visit the tree."
The tree was cut down in 2015 when it was in terminal decline and ready to collapse on the road and surrounding houses. This summer though, the energy in the roots have allowed it to spring new branches and come back alive. While not uncommon for a large cut tree to do this, it's still a wonderful story of rebirth.
I often need zero-centered color ramps in QGIS. Here is how to quickly make them:
- Open up the Layer Styling Dialog.
- Select the column you want to use and number of classes.
- Select the color ramp you want to use — typically a two or three color ramp — such as green-white-red or blue-white-red.
- Click classify.
- Note the highest or lowest value in the classes (such as -152 or 80).
- You will want to use the largest absolute value — in this case -152.
- Put in the column box, rand(-152, 152) and click classify. If you a using a simple shapefile without many objects, you may have to expand the range slightly, e.g. rand(-200,200), to ensure a full ramp is generated.
- Select the column you want to use. Do not click classify.
- You will now have a nice, zero centered, balanced color ramp for displaying your data.
One of the great questions faced by man kind -- but only recently answered conveniently and accurately -- is where am I? From precision agriculture to ship navigation to bus systems to navigation systems in cars, the answer to this question has solved many problems for mankind.
It wasn't all that long ago -- maybe 5 or 10 years ago -- when the average person couldn't just pull a cellphone out of their pocket, and find out their exact location down to 10 feet from their cellphone. Now such technology is common place.
The Transit Satellites, the first successfully launched today in 1960, started to answer that question. The transit satellites were primitive technology compared to the modern GPS satellites, but a necessary first step in man answering the question -- where am I?
Michael Minn's QGIS plugin adds a lot of great features to QGIS like export of KML files with the color table and attributes attached -- among other features.
The plugin is good but not perfect for KML exports, but it's remarkably helpful.
I'm honestly thinking about hacking the KML export options to make better KML exports (like transparency by default). I'm not a PyQGIS or KML expert but I think I could make it better -- and that's the spirit of open source software. We will see.
Earlier this week, I posted several maps of the 2015 Albany County Executive Primary race. After giving it some consideration, I decided last night to re-render the maps because they were not up to my quality standards.
I often like to experiment with new features, and while the shadow feature of QGIS can greatly enhance a map, it can also be a bit too much and actually detract from the readability of maps. I took off the shadow and re-adjusted the colors, which seemed to previously be too biased towards Egan over McCoy (the Egan colors were darker on a vote-basis on then McCoy).
I will post the enhanced maps over the next few days. I might experiment with other races. I don’t have a 2014 shapefile, but it looks like I can convert the numbers over relatively easily in Excel to match the EDs, possibly creating Super EDs as neccessary. We will see how nasty the weather is on Saturday, but that’s something I may with further over the weekend if the weather is bad.