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Trimble GPS Pathfinder Tools SDK Leveraging full GPS capabilities

Paul Manson
Product Marketing Manager
Trimble Navigation
New Zealand
[email protected]

A decade ago, Trimble Navigation recognized the need to make interfacing to GPS easy for professional software developers. Trimble realized that a toolkit was necessary for geologists, surveyors, utility engineers and legions of other users to have GPS capabilities integrated into the software applications they needed to do their jobs.

Trimble created the GPS Pathfinder® Tools Software Development Kit (SDK) to enable developers to seamlessly integrate GPS into existing applications or build entirely new field productivity packages. The ultimate goal of GPS Pathfinder Tools SDK was to empower developers and end users to fully leverage the flexibility and accuracy of GPS mapping within a familiar software environment.

The introduction of the Trimble® GPS Pathfinder Tools SDK has significantly benefited the worldwide community of mapping and GIS users-as well as the GPS industry-by stimulating demand for GPS technology. Availability of the SDK package has enabled software developers to add value to the basic GPS receiver and rapidly expand its application in hundreds, if not thousands, of vertical user markets that now rely on GPS for mapping, navigation and tracking on a daily basis.


In 1998, Trimble's highly successful line of ruggedized GPS Pathfinder GPS receivers had played a major role in developing what is now referred to as the mobile GIS market, comprised of professional end users whose livelihoods depended on the high-quality performance of their GPS receivers. One drawback to successful development of the professional surveying and mapping market was the standard NMEA protocol, which was and still is used by most GPS receivers. NMEA did not accommodate the coding capabilities for programmers to open the receivers up to the level of performance and functionality.

Without a toolkit and without using the NMEA protocol, the primary option for developers was to write code using the proprietary binary protocol for each GPS receiver. But this was not a practical alternative because the developers would find themselves re-writing the software code every time a new or upgraded model was introduced. Even in 1998, GPS vendors were updating their receivers about every 18 months, making it impossible for developers to keep their applications up to date.

Trimble saw the limitations of developing using the NMEA protocol as one of several weaknesses that had to be overcome for widespread professional deployment of GPS to occur. To accomplish this, the GPS Pathfinder Tools SDK had to be developed with the programmer in mind. Specifically, Trimble wanted its SDK to allow software developers to write their code once without having to worry about future GPS hardware releases. In other words, custom applications developed with the SDK would accommodate any Trimble device, past, present or future. Today, this remains the hallmark of the Trimble SDK. It provides seamless compatibility with the full line of rugged GPS receivers and handheld devices offered by the Trimble Mapping & GIS division, including the Trimble GeoExplorer® series, Trimble Nomad™, and Trimble Recon™ handhelds and the GPS Pathfinder series receivers.


Trimble introduced the SDK originally as an ActiveX® toolkit in 1998 and upgraded it to Microsoft® COM in 2004 to work seamlessly in the Microsoft Visual Studio® environment. In addition to providing multi-platform and receiver compatibility, the GPS Pathfinder Tools SDK overcame three critical NMEA weaknesses.

The first weakness was that the NMEA protocol offered users very limited abilities to configure their GPS receivers beyond what the outside buttons and dials could. The SDK opened the receivers up to the developers so they could access the inside of the devices and maximize the performance to meet the needs of specific end user applications and ensure they were collecting the most accurate data possible. For the first time, users could fully manage the set-up, control and status of their units.

By packaging the diversity and complexity of GPS functionality into ActiveX and then COM objects, the kit made it possible for developers with little or no knowledge of GPS or mapping to tap into advanced functionality. This in turn gave the end users a greater selection of settings and configurations to control real-time differential sources, establish radio and cellular communications links, and set accuracy thresholds.

Another NMEA drawback overcome by the GPS Pathfinder Tools SDK related to post-processing. NMEA doesn't allow for logging of raw data points for postprocessing with base station or other correction points back at the office. Even today, this is a potentially devastating problem for mobile GIS users because real-time differential correction sources are not always readily available or economically viable in all parts of the world. And even if they are, the professional GPS user typically wants to collect post-processing data while still in the field to ensure uniform data accuracy in case of data drop outs or errors. The SDK gives users the ability to log their raw data points and check their accuracy in the field.

The third major NMEA problem that the SDK was built to address is the issue of coordinate conversions. Because NMEA was originally intended for maritime applications, it only operates in latitude/longitude coordinates. For most mapping and GIS users, this means the data must be converted into a local coordinate system.

Although making this conversion is a relatively straight-forward process, Trimble found that many software developers unfamiliar with geodesy introduced errors into the calculations because they did not fully understand the impact that even the smallest errors could have on the overall conversion. To eliminate this problem, Trimble included a library of more than 900 local coordinate systems into the SDK along with on-the-fly calculation capabilities, resulting in extremely accurate coordinate conversions in real time.


The Trimble GPS Pathfinder Tools SDK supports industry-standard Windows® operating systems, including Windows Mobile® software. Its use of the COM interfacing technology means that most experienced developers work with it seamlessly in Visual Studio. COM has also enabled Trimble to create a wide variety of programming objects the programmers can access to integrate complex GPS capabilities into their applications with minimal GPS familiarity.

Integrated as standard features into many professional applications, these GPS capabilities extend tremendous advantages to SDK developers and their end users. The following is a summary of the key capabilities made possible by the GPS Pathfinder Tools SDK. Full GPS Accuracy Control-For most GPS users, the ultimate goal is to collect location coordinates with accuracy that meets the needs of their specific application. These accuracy parameters vary from one industry-and often one project- to the next.

The SDK allows the developer to give the end user the ability to easily define the accuracy thresholds of their project so the receiver can essentially configure itself and eliminate the guess-work and some of the decision making from the end user.

Control over Differential Correction Sources-As noted above, accuracy is the ultimate goal, and for many mobile GIS applications, differential correction plays a role in data collection. Because differential correction can be quite complicated and require on-the-spot decision making by the end user, the SDK simplifies the process to put the user in control over this aspect of configuration.

The end user's selection of differential correction source is usually dictated by financial considerations and availability within a specific geographic region. Most users will select the free alternative when it's available. But these options vary with location, and the user typically wants to make that decision. The decision may also involve selection of which communications method (cellular, WiFi, etc.) will be used.

The GPS Pathfinder SDK allows to take this into account by setting up simple interfaces where the end user can enter their correction preferences, including access numbers and passwords. In the field, the user can quickly select the best option from an interface list so the most accurate and most affordable one is used during that session. The developer can also program in a set of rules as a default by which the receiver can choose the correction source according to user specifications.

Raw Data Logging Control-As noted earlier, the majority of mobile GIS users want to log their raw data in the field so they can perform post-processing later. Even when they don't plan to utilize post-processing, the procedure may be necessary if errors occur. With this in mind, SDK gives the end user the ability to select whether raw data will be logged or not. Most organizations choose to enable data logging during the initial receiver set-up and then forget about it. That ensures the data is there if it's needed.

H-Star Data Collection-Trimble introduced the H-Star™ data collection technology for subfoot accuracy in 2006 for the line of GeoXH™ handheld and GPS Pathfinder ProXH™ receivers. With three base stations operating within 125 miles/200 kilometers, this technology enables the devices to easily and quickly acquire location data from one foot down to less than an inch, the desired accuracy for most GIS mapping today. The SDK allows programmers to integrate this capability directly into mobile applications.

In the subfoot mapping environment, the correct setting of certain GPS parameters, such as selection of appropriate differential correction sources, become exceedingly important. The GPS Pathfinder SDK toolkit gives developers and end users the ability to access H-Star technology to maximize efficiency and minimize cost. This makes the Trimble Mapping & GIS receivers the easiest devices to use for collection of subfoot GPS data without transitioning to survey-grade equipment.


The Trimble GPS Pathfinder Tools SDK has become known as the toolkit developed by programmers for programmers. Its ease of use and excellent support along with its royalty-free terms have made the SDK extremely popular among worldwide third-party developers of mapping and GIS packages. Trimble estimates that nearly 80 percent of active SDK purchasers are using the product to create outside applications for re-sale, mostly within vertical market segments. The remaining 20 percent are developing customized inhouse applications.

The vast majority of third-party packages are being built for mobile applications running on handheld mobile GIS devices with integrated GPS hardware. Trimble believes that many of these applications serve users in the utility, government and architectural/engineering/ construction markets, which are the major segments of the company's overall client base.

When asked why developers chose the Trimble GPS Pathfinder Tools SDK over other products, they typically responded that they like the fact their code is compatible with all Trimble GPS receivers and platform.

Secondly, developers appreciate that COM hides the complexity of GPS inner workings and coordinate conversions in simple objects so they can focus on creating the application without having to keep up with latest GPS technical minutiae.