Do You Need RTK and Drone Mapping? Is it worth it? Check out this article to find out all the benefits that this technology has to offer.
RTK, expanded as Real-Time Kinematic is a buzzword even many pilots in the UA industry do not understand. Even those that are mapping with a drone fail to understand this term.
Talking about RTK in relation to drone mapping, we need to understand how the technology comes to work. Drone service providers may also want to know if it is possible to earn more money with RTK.
In this post, I have covered RTK technology and drone mapping elaborately. During the course of this discussion, we will also explore if drone service providers can earn more money with the help of RTK.
Do You Need RTK and Drone Mapping?
What is RTK capability?
When a manufacturer says their drone has RTK capabilities, you can’t jump to the conclusion that you can use their drone to start surveying businesses.
You must first understand that owning an RTK aircraft is not a sufficient reason to become a surveyor.
Depending on your area of interest, a degree course in surveying can take up to four years to complete. You will also need at least six years of time in the field and a pass in the land surveying examination to qualify for a surveying license.
The use of UA is gaining immense popularity across several domains. Though accuracy and precision are not difficult to achieve with RTK drones, you must know that there are different levels of accuracy and only a survey grade accuracy can be useful for professional applications. Also, the term survey has different connotations in different missions.
While fields like architecture, engineering, and construction can accept accuracy in tenths, surveyors actually get to work with hundredths or thousandths of accuracy levels.
You must know that this highly matters since while dealing with UA, you must know the degree of precision you can expect from an aircraft and its accompanying system.
While addressing a conference, a presenter claimed recently that their dual RTK aircraft can ensure an accuracy level of less than 1/1000, which is a dubious statement as much as our knowledge of the technology goes.
Let us try to understand how RTK works and why it is important in drone services.
Mapping Vs Surveying
In the first place, we must clearly understand the difference between mapping and surveying.
A UA system can help create a localized or flattened image of a given ground area. Such an image can provide measurable data with a given degree of measurability.
Many factors can impact the levels of accuracy including the altitude of flight, image sensor’s size, lens’s curvature, shutter to antenna latency and many others.
In surveying, a localized drawing or image of a given ground area that contains measurable data characterized by accuracy and precise measurability is created.
Going farther than the scope of this discussion, we must understand that in a construction survey, a greater slip in precision is allowed than in land surveys. Aspiring drone service providers must understand this also.
RTK aircraft receive the necessary corrections from a familiar grid system using a few different kinds of technologies. With this, the aircraft can precisely know where it is positioned in the XYZ space with regard to its ground locations.
RTK drones receive such corrections during their flight and write them to the Metadata featured in every photograph they capture. This data is in turn imported into a processing software of their choice like 3DR, Pix4DMapper, and Leica Infinity, which localizes the data.
If all the parameters are set properly, the localized data can be measured with great degrees of accuracy.
How does an RTK aircraft capture aerial position?
NTRIP is a service provided worldwide. You can understand this as Networked Transport of RTCM through Internet Protocol.
For the sake of using this kind of correction, you will need a cellular modem, a cellular data plan and a receiver that can accomplish RTK correction.
Some state or municipal services provide the NTRIP data connection free of cost. In some cases, a nominal annual fee is collected.
RTCM containing the correctional information is used for the transmission of NTRIP data. The NTRIP server is always in contact with GNSS nodes that are around several regions of the US. This server broadcasts GPS data via WiFi all the time.
This system is used for wirelessly transmitting data to different kinds of industries. For instance, some of the industry segments that heavily use NTRIP include agriculture, different departments of transportation, engineers, surveyors, area inventory management, and driverless cars.
The NTRIP stations also known as nodes are installed at known points and they constantly stay connected to satellite location data.
The collective nodes send the data to a server that does the job of aggregating the location data in between the satellites and nodes and keeps sending out a correctional data stream which informs the rover device where it is exactly positioned in the XYZ space.
This information is highly accurate to the point of 1 cm or .39’’ horizontally and 1.5 cm vertically. We can say such an amount of precision sufficiently meets the needs of aerial precision work.
How is accuracy measured?
Whether you are using only UA and a base station correction system or an NTRIP correction system, first you will need a point you are familiar with.
You can capture them with the help of different kinds of GPS systems like the DT Research 301, an elaborate system like Leica GS18 receiver, Hoodman Ground Control Point system fitted with a rod and bipole, or an Emlid RS2 Base or Rover system.
The Ground Control Points, also known as controls can either be mobile or may be painted on the ground.
An exclusive kind of nail that has grids for precision is nailed to the ground and spray paint is used to mark the area. When walking or flying it is required to find the nail rapidly and to this end, paint is applied.
This is a special kind of surveyor paint, which you can buy in most stores dealing with surveyor specials. It is most common to find this paint in cases containing 12 cans.
The point that is familiar to you also known as the check will have to be compared relationally with the data that the UA provides. Ellipsis of error is marked by the difference.
Different tools like Pix4D and Leica Infinity can demonstrate the differences with regard to the location. For a general understanding, the data supplied by the aircraft must be within 1-2 cm of the familiar point when captured from a static position.
Sometimes, you can take the help of a county or state system to access these known checkpoints, which have recorded certain known monument points that a professional land surveyor has set.
Precision and accuracy can be ensured only when several parameters are ably met. We can explain precision and accuracy with the help of some examples.
Let us consider an image that is captured from a UA that is flying at 75’ in altitude. Without correction work, projecting it where it is in no way different from projecting its position locked to the ground and this can be done accurately.
In this case, the accuracy level is a bit greater than the accuracy of a cellphone’s GPS system and hence not highly dependable.
In some typical cases captured with a Leica GS18i for instance, the projected point can be around 10’ off from its actual position.
This amount of accuracy is rather not highly useful in any type of survey or construction environment. When the UA does not have RTK capability, this is the amount of accuracy that a UA will provide depending on the type of sensor, altitude, and speed.
If an RTK antenna system is applied to a flight connected to a base station or NTRIP, the typical difference between the projected and actual positions can be around 18.5’’.
Though this amount of precision is close to what most kinds of works demand, they are still not close enough.
In most cases where a base station or NTRIP are applied in flight, the difference between the actual and projected points can be around 1 cm. Most commercial applications require such an amount of precision.
Is it possible to earn more with RTK drone, base station, and NTRIP?
In general terms, it is possible to earn more with RTK drones, NTRIP, and base stations. To provide services to a survey company, you must have enough experience.
Irrespective of whether you will serve an ALTAs, or the land or construction industry, how much you will charge for these services will depend on how much time you put in, the kind of improvement you do on demonstrating data, and the host of other benefits that UA brings.
How to ascertain the accuracy of the coordinates?
To ascertain the accuracy of coordinates, you must have the necessary understanding of mathematics and coordinates.
To determine localized truth, different companies resort to different means. While some of them can be regimented, some are informal and involve only a handful of checkpoints.
When it comes to verifying the level of accuracy, The American Society for Photogrammetry and Remote Sensing (ASPRS) offers guidelines on verification of accuracy, most of which are beyond the means of a typical UA pilot and their equipment.
Important aspects of the Positional Accuracy Standards of ASPRS
Accuracy is gauged by the RMSE, otherwise known as Root Mean Squared Error taking into account the difference between the points measured independently and the modeled points.
To ascertain the accuracy in an accurate way, checkpoints that were not included in the production of the model have to be used.
Ground measurements have to be done with the help of an independent source that is more accurate than the aerial mapping system.
Horizontal and Vertical accuracy must be gauged independently and depending on vegetation, it can have different kinds of properties.
Can I be a surveyor if I have an RTK aircraft that gives precise results?
In most states, you will need a license given by an accredited program or testing system to become a surveyor. For eligibility, candidates must have passed the FS (Fundamentals of Surveying) exam, PS (Principles and Practice of Surveying), and an exam specific to the state.
For information regarding the state-specific examinations, you can check with the licensing board of your state. In addition to testing, a few states need only a high school diploma.
What are the other uses of an RTK system than surveying?
Surveying with RTK drones are highly sought after in precision-focused environments across different industries. Therefore, UA pilots, contractors or surveyors can hope to find ample opportunities in this segment.
When deployed properly and managed well, RTA workflows can be depended on for providing precise data. Whether it is DTM, Contours, DEM or just a simple kind of ortho, this is a sure benefit to anyone using any of the different kinds of mapping.
It is important that you know localized data and how to scale it for providing measurements, whether for reconstructing the accident scene in the interest of public safety or to determine the corners and boundaries with regard to land development.
Jon is a passionate photographer and videographer who has been flying DJI drones for over 5 years. He loves the freedom and creativity that comes with capturing aerial footage and the unique perspective it provides. Jon is always on the lookout for new locations to explore and capture with his DJI drones. His favorite DJI drone is the Mavic 2 Pro, which he uses to capture stunning 4K footage with its Hasselblad camera. Jon is always eager to share his knowledge and experience with other drone enthusiasts and is a member of several online drone communities. When he’s not flying his DJI drone, Jon enjoys hiking, camping, and spending time with his family.