Using Google Earth to obtain NGS CORS site information

Every now and then I come across some little utilities that help to make things easier while working in the field and these pages are mainly my way of sharing them with others while creating a go-to place where I can easily find them when I need them.

Here is a Google Earth file that that contains locations and basic information about all of the National Geodetic Survey (NGS) Continuously Operating Reference Stations CORS. Saving you time from searching for CORS stations in your area and finding out what sampling rate they record GPS data at.

GPS Calendars

GPS or GNSS Calendars are different then traditional calendars that most of us are used to working with, yet they are pretty common these days due to the increased use of GPS equipment. Yet there is never one around when you need one, so if you find your self doing a lot of GPS field work like myself then you may notice that you will working in Julian Days & GPS Weeks frequently so will want to print off your own copy or use an online utility to help you out.

For those new to GPS or GNSS Calendars: Julian Day is simply the numeric number of the day in that given year, example March 5th of the year 2013 would be the 64th day of the year with a julian day of 064 and a GPS week of 1730. The GPS Week # would be 17302 (the # 2 on the end represents Monday from the formula Sunday=0, Monday=1, Tuesday=2, Wednesday=3, Thursday=4, Friday=5, Saturday=6).

Now one can easily calculate this info but I find it quicker to just resort to reference pages or use online utilities and here a few that I use:

2013 NOAA GPS Reference Calendar or Canadian Spatial Reference System GPS Calendars (provide PDF versions but do not yet have a 2013 version available) for printing reference pages

– Here is great little online interactive GPS calendar utility that I often use, simply click on a date in the calender and the utility will show you the corresponding Julian Day, GPS Week and GPS Week Number for various years.

2013 GNSS calender


Converting between UTM, MTM and LAT/LONG

Canadian using a UTM map

Geographic coordinate systems enable us to spatially locate features on the Earth using specified set of two dimensional numbers. The coordinates of each feature represent the horizontal position (and sometimes vertical position when elevation is available) of it and one of the most commonly used coordinates is Geographic with values of latitude, longitude. However many different coordinate systems can be used to map the same area depending on various factors such as map extent, scale, end user etc. Therefore we often find in Geomatics that we can have data from different coordinate systems that we need to use together spatially in one reference system.

I am sure that most of us have run into times when we have features that have defined coordinates of one system that we need to use with a different one. (E.g. your map is in UTM (Universal Transverse Mercator) but you have been given GPS points in Lat/Long).

If you ever find yourself in need of quickly getting values converted from Geographic to UTM / MTM (Modified Traverse Mercator) or UTM / MTM to Geographic then here is a a free online geographic coordinate convertor tool that I often use provided by Canadian Spatial Reference System

Precise Point Positioning GPS Processing

Sometimes when doing GPS field work I will often require a way to double check my own GPS Processing work or am sometimes too far from an active control network to tie into. Using Precise Point Positioning or PPP service in these situations has often come to my aid, especially on jobs in Nunavut or in Northern Ontario.

Natural Resources Canada’s Canadian Geodetic Service provides a free online global GPS processing service called Canadian Spatial Reference System – Precise Point Positioning (CSRS-PPP), where you can process files containing RINEX (common Receiver Independent Exchange Format that is used to exchange GPS data between various software and hardware) observations from either a single or dual frequency receiver in either static or kinematic modes. The service is free but does require that you sign up to obtain a username and password to gain access.

Once logged in, you upload your GPS file and basic info, then you will receive an email containing corrected coordinates (latitude, longitude, ellipsoid height) in either NAD83(CSRS) or the ITRF reference system. It also applies the HTv2.0 height transformation and produces orthometric heights compatible with CGVD28 elevations to your data.

PPP results generally are more accurate when recorded over a span of several hours, so I tend to let my receivers run longer if I know that will be using PPP.

“PPP accuracy improves with the length of the data collection period. A minimum period of good quality GPS data is required to permit convergence and resolving ambiguities which in turn can improve the accuracy of the entire dataset. The minimum period and the accuracy attainable will depend on the type of GPS equipment, the site (multipath, obstructions) and atmospheric conditions. Extending the data collection past this minimum period should further improve accuracy, but more so with dual-frequency receivers than with single frequency”. See for more information.

PPP Direct utility for Windows 7

The Canadian Geodetic Service have also created a PPP Direct utility for Windows 7 (note: I have not tested it yet) where you can Submit your GPS data for PPP processing without logging on to the web site. The PPP Direct utility lets you ‘drag and drop’ RINEX files onto an icon where it is then immediately submitted for CSRS-PPP processing (so an internet connection is required).

The login to begin PPP processing or to download the PPP Direct utility installation file is and a detailed PPP handbook covering all the basics of the service can be found here




Geographic Information Systems (GIS)

Geographic information systems commonly known as GIS has become a rapidly growing technological field that allows Geomatics Specialists to solve and model real world situations by incorporating digital spatial and associated tabular data. It is often defined as a comprehensive computerized information system made up of hardware, specialized software, spatial data and people to help manipulate, analyze and present the information used for storing, manipulating and analyzing spatially indexed information.

Geographic Information SystemsGIS operates on many levels and over the past decade has become an essential tool for most urban and resource planning and management organizations. On the most basic level, GIS can be used for simple digital cartography, to create various types of maps.

However the real power of GIS is through its abilities to use both spatial and statistical methods to analyze attribute and geographic information together. The end result of such an analysis can be vast amounts of derivative information, interpolated information or prioritized information.
Geographic information systems commonly known as GIS has become a rapidly growing technological field that allows
Geomatics Specialists to solve and model real world situations by incorporating digital spatial and associated tabular data. It is often defined as a comprehensive computerized information system made up of hardware, specialized software, spatial data and people to help manipulate, analyze and present the information used for storing, manipulating and analyzing spatially indexed information.

GIS technology can be used for scientific investigations, resource and utilities management, modeling, assessments, development planning, cartography and route planning and many other applications.. Some of these and other aspects of the GIS field are currently covered on this web site including projects related to spatial database modeling, Geostatistical spatial modeling, mobile mapping, cartography, and interactive web mapping.

Below are some examples of GIS from a few of the many GIS based projects that I have been involved with over the past few years. The links are to PDF versions of papers, presentations and or manuals related to GIS, I have many more, if anybody is interested in a particular topic then feel free to let me know, as I may have a document available related to that topic.

Examples of GIS


TITAN Mobile LIDAR Scanner

Mobile laser systems use a GPS-IMU (global positioning system – inertial measurement unit) combined solution to help track where the LIDAR scanners are located while they are operating during data acquisition. LIDAR processing software is then used with GPS collected data (from a GPS unit setup over top of known high precision point) to calculate the spatial locations of each LIDAR point located within the point cloud that represents 3D real world objects.

TITAN Mobile LIDAR scanner

The TITAN mobile laser scanning system is a custom made robust vehicle mounted mobile scanning solution. The TITAN system incorporates an array of 4 separate Riegl laser scanners to provide a 360 degree field of view. The laser scanners are combined with a GPS unit and a high accuracy aviation grade IMU, then mounted inside a custom pod and raised 12 feet in the air using a heavy duty custom made scissor-lift style boom. The mobile scanning unit can be operated from within the moving vehicle and collects over 50 points per square meter while moving at speeds of 70-80 km/hr (slower speeds produced more points).

I have been operating and managing LIDAR projects using the TITAN mobile laser scanning system for over two years now, in a variety of projects from coast to coast (and hope to include some info on these trips and some sample sample data screen shots soon).

LIDAR GPS Validation

Summary poster created to show GPS validation data collected for 2003 LIDAR survey of the Annapolis Valley. Poster was one of several presented at the Geomatics Atlantic 2003 Conference held at Acadia University in Wolfville, Nova Scotia and posted at the Applied Geomatics Research Group seminar room in Middleton, Nova Scotia.

The Impact Of Modern GPS On Transportation & Society

GPS technology has been around a lot longer than most people give it credit for. Just a couple of years ago, The Atlantic did a write-up about Roger Easton, the man credited with much of the creation of early GPS and said that his work began in the mid-1960s. At the time, GPS was meant more as a means of tracking satellites during the space race than for pin pointing our own positions on Earth. And that only makes the technology’s evolution all the more incredible.Now, not even a decade after the smartphone revolution took off and put GPS into the palms of our hands, GPS is taking on another new purpose.

Most of us started to notice or care about GPS once it started being packaged into devices that we could put in our cars for purposes of easy routing information. This development, as well as the emergence of tools like Google Maps and Apple Maps on smartphones, turned GPS into a personal tool that individuals use on a day-to-day basis.

Now, not even a decade after the smartphone revolution took off and put GPS into the palms of our hands, GPS is taking on another new purpose. The growth of more sophisticated GPS technologies has led to the birth of the telematics industry. This industry is the idea of using computers and mobile technology together to improve the management of vehicles and even the environments around them.

What may first come to mind when you hear about telematics is the idea of self-driving vehicles, and that’s where modern GPS is having some of its most significant impacts. The use of “differential GPS” has improved location tracking to centimeter-level accuracy, which has profound implications for the coming autonomous driving movement. Instead of only using signals from satellites, this new brand of GPS can also pick up on reference points on the ground, ultimately compiling all of the data to make for a more precise picture of location. This sort of technology, working in conjunction with an array of other sensors on a vehicle, is what will make self-driving cars possible (and safe).

If GPS is enabling self-driving vehicles, it’s also important to realize the scope of that impact. We tend to imagine things on a personal level when this topic comes up, and who could blame anyone for doing so? The idea of getting into your car, telling it where you want to go, and sitting back to enjoy the ride seems like something out of a science fiction film, and it’s still hard to believe that we’re on the cusp of this vision becoming a reality. But GPS-enabled autonomous vehicles have far broader implications than simpler and more relaxing daily commutes.

On the one hand, we should also consider autonomous driving as it relates to industry. Large companies with expansive shipping fleets are already starting to implement “smart” features in their vehicles in order to ensure safer and more efficient transportation of goods. If the trucks on our roads are run by advanced GPS and autonomous driving systems in the near future, it stands to reason that shipping operations will become quicker and more reliable, possibly resulting in more affordable products. Fleet vehicles will also likely be practicing safer habits, making our roads a little less hazardous.

Additionally, the advanced GPS and smart features in autonomous vehicles also have the potential to significantly change our urban environments. A smart car interacting with its environment enough to navigate on its own is also sending data out regarding its location. This can (and will) result in automatic traffic monitoring, such that people will be able to get a clearer picture than ever before of what the streets will be like at any given moment. For that matter, we may even be able to look at an app or a public guide of some kind and see where there might be an open parking spot!

GPS has a great deal to do with ushering in the transportation of the future, and the way things are moving lately, that future may arrive sooner than most anticipated.