We are hey everyone and welcome to another interesting episode of ask drone you. Thank you very much for being here with us. Listening to other shows thank you for supporting the show through membership. If you are a droneyou member, if you are not a droneyou member, you can become a member at the droneu.com forward. Slash become a member and you just add hyphens between become a and a member. But that said, uh very grateful that you are here joining us today. As always, and as always, my name still starts with a p still ends with an l, and you can call me paul indeed and im still rob and uh yeah glad to be here with you and looking forward to doing some shows thanks for joining us yeah. Thank you very much um. We have a very interesting show today, uh very uh, if youre into mapping, i think youre really gon na, like this, its like really driving into detail uh regarding uh geo, referencing and absolute accuracy versus relative accuracy, very interesting and specific question. Uh and it actually comes today from mexico – and i have to say rob when i was in mexico in 2016 – doing some drone work. It was uh. The most active drone location id ever seen, uh pretty much. There was a drone over every construction site in cabo san lucas. I mean back in 2016.. Yeah yeah lets talk about wild wild west seriously, but i mean it just goes to show how, when the the value of drones is understood, um clearly that theyre deployed often you know absolutely, but that said uh todays show is brought to you by drone.

You launch a brand new educational platform, its really built to make the lives of drone programs and managers much easier, because you can manage and delegate all sorts of nuanced training, verticals and know exactly when your well pilots have completed. Certain steps have actually proven their currency and proven their proficiency, and this is a great opportunity because we have a mapping question today to tell everyone. If you are a droney member, you do have access to our comprehensive mapping class. In 2019, we refilmed that drone mapping class added a lot more information to it. I think it added about three or four hours of content to that class, and that is now available through the drone. U props mapper platform and that mapper platform also includes the dont crash course. Operations course. Maintenance course flight over water and some other mapping related courses as well, but remember with props its all about professional, reliable operators practicing safety, so its really a comprehensive program, a step by step, hold your hand, sequential training that you really cant mess up and youre even Rewarded as the training is gamified because, as you pass certain quizzes, you are actually given resources and shortcuts to make your life easier. If youre ready to dive down the mapping hole as a single operator or youre trying to build a drone program to essentially provide mapping deliverables youve got to check out the props mapper platform. You can go to propsflightschool.com or props.

thedronyou.com hi. My name is eduardo. First of all, i just wanted to say thank you guys for all the contents. You post im fairly new to drones and still trying to catch up on your other videos, im looking to get started with the drone mapping business in mexico. I currently have a phantom 4 version 2.. My processing software is pix30 mapper im, currently using a total station for mapping. My question is: is it completely necessary to have a gnss receiver to layout ground control points, or can i do that arbitrarily with coordinates? In my total station, if geolocation isnt my goal – and there are no reference, points nearby im still looking to get centimeter position or could that simply be achieved in the processing program, with horizontal and vertical constraints? Once again, thanks for all the help and all the advice you give to the community, thank you eduardo great question and uh love the way you asked actually good detail and i think youre kind of excited to answer this one actually yeah. I was excited uh to answer this one and i am excited to answer this one uh just because, as many of you know, i i really love drone mapping its one of those few verticals in the industry. That requires great technical skill, but also creative intuition to complete certain jobs, so yeah absolutely rob its uh its something i thoroughly enjoy. Um, in fact, were actually having another mapping class here at hq in november, the 17th through the 20th.

If you want to join us for an in person class, so lets go through this question really quick eduardo. I just have to say i agree with rob 100 on the eloquence in which you ask that question. So, just just to make sure i have it clear. He rob, it seems like he is asking uh kind of, as we discussed in pre show right uh that he that he essentially needs centimeter precision, but geo location is not important. Uh. I like the way you described it in terms of your can relative to your computer relative to the world yeah. So lets do that again. So essentially, what i think the real question is is is really a differentiation between absolute accuracy and relative accuracy right so to essentially go down the same rabbit hole. I did in pre show with rob what i think hes asking for is look. I need centimeter grade accuracy, but not geo located. So essentially, i need to know how far this can is from this laptop. I dont need to know where, in the world that is so absolute accuracy is essentially how accurate is your map in relation to the real world, whereas relative accuracy is essentially how accurate is one objects distance to another objects. Distance essentially in the map, so is like. If i know that the distance between the can and the laptop is two and a half centimeters, am i going to get that same relative accuracy uh in my map? So i just want to make that that clear first, because it sounds like hes after relative accuracy and theres a couple of things.

I also want to go over just to make sure i i hit them really fast, rob um. That is, you know he talks about. Hes got a total station and he asked do i need a gnss receiver. I think this kind of goes back to the whole, having um a a fixed point or a fixed total station and then having what we call a gnss rover that essentially speaks with that total station, so that we can get like essentially, a double form of accuracy And i mean absolute accuracy now a couple of things. One thing i picked up on and im not sure and eduardo. Forgive me im not im, not saying you lack information im just trying to better understand um, but it sounds like based off of his question regarding the gnss rover and the total station that there may be some confusion about ground control points as a whole. Which brings me back to ground control points in photogrametry in drone mapping are two parts, one part gps, so knowing the actual point in the world and then the second part is the target, the ability to see that target and that point 100 feet in the air. So that you can adequately mark that point and actually geo locate the map as a whole. Now that said, you can utilize a total station to mark gcps and gather geo referencing. It is a more cumbersome and complex process, typically total stations output in an arbitrary coordinate system.

So ive seen some students really struggle with taking that arbitrary coordinate system and converting it into a known, coordinate system im not really sure what the standards are in mexico. So lets just say that he uses wgs84 uh, which is the world geodetic system uh the one that essentially your drone takes photos in its that coordinate system, and so i dont know if hes asking can i use just the total station? Do i have to have a gnss receiver rover with my total station or uh you know. Can i just use nothing right if hes after, if hes after relative accuracy and hes, not after actually geo referencing the map as a whole, then the answer is you dont? Need any of that stuff, because if youre not geo referencing the map, then why would you need gcps? Okay now that said, can he geo reference a map with just a total station uh? The answer is semi. Yes, uh. You would still need some sort of target on the ground again. That target is really supposed to be 40 times gsd ground sampling distance. So if hes going for a centimeter, we want it to be at least 40 centimeters uh with length so that we can really ensure that we mark our points in the most accurate means possible because theres still an issue with the human error. The ellipsoid error, the projection error, uh, that that drone pilots can inject to maps to make them more error prone, but lets talk really quick about if we are just creating a map, slash model and it does not need to be geo referenced.

What can we do to ensure a high relative accuracy, meaning the the can of t is? Actually, you know a stated distance from my computer and make sure that our map slash model showcases that hes right about using scale constraints, but i dont think his question by the way. I appreciate the question. I dont think the question paints the full picture or is adequate because he talks about horizontal and vertical scale constraints, so heres heres robs mapping test. I dont mean to put you on the spot, but on the spot, lets, do it how many axes of gps? Are there three perfect, perfect answer? Okay, taking that answer and applying pauls logic into asking you questions: oh no, wait a minute logic: okay, gotcha! Okay, knowing that there are three axes of gps, what do you think is the minimum number of scale constraints that we should have in any given uh map or model? Three perfect answer: yes, thats correct now, normally in order to ensure relative accuracy across the entire map, you would need multiple scale constraints, because we have found uh thanks to mr on good, seeing who no longer teaches photogrammetry uh, but we have found through data agreed on That point uh: we have found through data that if you have scale constraints or gcps more than 500 lateral feet from each other, you do get a reduced relative accuracy. Okay now another thing to note: if eduardo decides to do lets, say a double grid acquisition plan, and then he does like orbital data or uh oblique data or something else outside of the autonomous data that will actually reduce the relative accuracy.

When you add multiple flight plans over one another now you can eliminate that problem with manual tie points but its not always fully eliminated. So that said, assuming the relative accuracy goal of lets say a centimeter or two centimeters. He has got to fly one very low. Two hes got to make sure he did a compass calibration uh in a place without magnetic interference and done correctly to reduce essentially any error from the aircraft itself. He also has to ensure a very high level of overlap, and he really needs to stick with one acquisition plan which uh dependent on what hes mapping lets say that he is in a even a semi urban environment. I still recommend a double grid. I really do. I think, even with a 70 degree tilt hes gon na be fine on the relative accuracy, its when we add in those higher levels of obliques that the relative accuracy goes down on the overlap. You set a high level of overlap. What is a high level? So, typically, a standard level of overlap that we teach through our comprehensive mapping class is a 75, so 75 frontal overlap 75 side lap for what hes trying to do um, i would say, maybe an 80 80.. You know anytime, you go over 80. You really add a significant amount of time in the air. I would think 80 adds a lot of time, but its definitely gon na add time thats for sure.

But i got you: okay yeah, but at least hes got the right drone to do the mapping um. So that said, if i understand the question correctly, which that could be wrong um. But if i understand the question the question correctly, geo referencing is not important. He still wants to get a high relative accuracy. Hes got to fly very low if he has undulating terrain. He has to use terrain awareness, okay, he cannot fly at multiple altitudes because thats going to inhibit the relative accuracy, hes got to add scale constraints. What i tell people with ground control points and to make this illustration better, is that um? You really want to add ground control points like tables of a leg or excuse me, like tables of legs like legs, of a table im. Obviously, havent woken up yet um like legs of a table and in order to get the best geo, referencing or even the best relative accuracy when it comes to lets, say using scale constraints instead of gcps. You still want to essentially uh distribute those scale constraints across the mapping area like legs of a table. Okay, so in his in his um goals of high relative accuracy, i would recommend, say nine scale constraints. Maybe i mean really if we really want to do our job here, we want to do 12, okay, um, but i have found that oftentimes its not necessary. So what he can do is he can take lets, say a tape measure um.

He can also use real world objects. Remember scale. Constraints are supposed to be on flat areas, theyre not supposed to be in shadowed areas, because if you create an mtp over a shadowed area, it tends to move so that injects air. So that said, what he could do is lets say he had a scale constraint here. He had a scale constraint and like over here im pointing to one corner of my laptop and then on the opposite corner. He had a couple and then maybe a few distributed in the middle. The hardest thing is the vertical scale constraints, which is something that i wanted to develop here at droneu for a while is a vertical scale constraint, because when it comes to scale constraints, you really want them to be 20 feet or more. The bigger the scale constraint, the more accuracy relatively that you will get. Okay, the smaller the scale constraint, the less opportunity for correction. So um that said lets say: hes got multiple scale constraints set up like a leg of a table. Hes got a couple of vertical scale constraints and uh. Hes got him distributed properly as long as he flies low. He does the image acquisition properly. He should be able to get a very high relative accuracy, but this is another important point to talk about that. We talk about in the um, the mapping class. I call it my. How do you know youre being lied to at a conference? Uh port module so its a very short module, very short module, uh yeah about five minutes, but no, i always go back to you know when i was teaching at the pix4d conference in denver a couple of years ago.

There were, i think it was 250 or 300 people at the entire conference, and i literally had 80 percent of everyone in my talk right, which i felt really really really good about. I felt really bad for bill english, though, because he was speaking at the same time in the other room and had very few people, so i feel like ive, stolen bills, thunder so sorry bill im sure hell get you back, yeah im sure too, but that said There was another talk right after his which was like how you can get one millimeter accuracy, and i always talk to my students in class, and i say: do you know how we know for a fact that he is lying and and every once in a while? I get a student who raises their hand and theyre like we know, hes lying, because, whether its relative accuracy or absolute accuracy, your accuracy, is only as good as your gsd, your ground sampling distance, your ground, your accuracy, can only be as good as a multiple of Gsd so lets say: gsd is an inch, relatively speaking, were going to be good at 1x to 3x, our gsd. So because most people are just taking 20 megapixel images flying at lets say a hundred feet. There is no physical technical possible way in hell that someone can get a one millimeter accuracy. What about on earth im just kidding um, so so explain to the folks quickly how theyre going to get that gsd down so ground sampling distance, as we talked about in the show here a couple times also in the props mapper class uh, which we go in Very very minute: detail about ground sampling.

Distance is a factor of three variables sensor size, so theres the sensor size of the camera, the altitude that youre flying and the focal length of the camera. Okay, typically, the best means of uh reducing the ground sampling distance is by lowering the altitude but theres only so low that you can go right. Most apps its like before you hit the building that too right, yeah yeah, most apps, the lowest you can go, is like 60 feet. Okay, i didnt know that which, if i remember, is like the equivalent of like half a centimeter, i cant – i i dont, have the calculator in front of me. I mean i technically do but im not pulling it up, but that said, if he wants to get the one centimeter, not millimeter one centimeter accuracy, hes got ta fly really low and really low is 80 100. I would have to out here thats okay, you know yeah, i didnt mean to have you do that, but um well heres a trivia question. While i pull this up, okay, how many centimeters are in an inch isnt? It like three point something: two point: five, four. Two point: five four should be able to figure that out from like doing yeah, never mind im, not even going to go there. Well, we bring this up because if gsd lets say is 0.35 inches at a hundred feet, would that get us one centimeter 0.35 would be like three yeah.

Yes, it would. It would be a little under so about a hundred feet. Is this maximum altitude? Okay? So thats, if hes flying a phantom 4 pro version two which see i have it, set up in the calculator right there yeah so now. This is also really quick talking about the future. This is why im so excited about the free fly. Drone the sony air peak drone because now youre taking a sensor, thats much larger right and its 42 40 50 megapixels ish and you dont have to fly as low to get the same quality so youre in the air for less time right. You know, but it does give you the opportunity to get even better quality if you do continue to fly at 100 feet 100, whatever, which is kind of exciting, too 100 yeah 100. So im very excited because these new drones, whenever the hell they do come out. Uh seriously, what a joke uh, but whenever they do come out, the efficiency that drones give in construction in volumetric measurements for quarries, for landfills, for public works for planning the efficiency is now going to be off the charts. I mean literally the time that its going to take to acquire the same data will be half the one thing that i would warn everyone when you are selecting a newer drone in your mapping. Business is be careful that your camera sensor does not go over 50. Megapixels, okay, thats important because youre going to have to pay more money to process said imagery, thus decreasing financial efficiency.

Really, yes, me, i yeah, okay! I just take your word for it. Well, thats the case on pix40 mapper uh. I know its the case in other softwares as well. I dont know off the top of my head all of them, but for vast majority and hes using pix4d mapper yeah, he will pay more money for a 50 megapixel shot. Now its also important to note like the a7r 4 – whatever i believe, is rated at 60 megapixels, but i think thats raw, and so, if you shoot a jpeg, it should go down. I forget how much the megapixel count goes down because it crops in from the edges um. So i i dont know exactly what that crop factor is. That said, it is an important thing to know if youre out there looking for a new uh new drone to buy very interesting meaning you have to get a different version of mapper, a more expensive version. Expensive version no kidding interesting, yeah, wow yeah. I feel weve learned a lot today. I feel like i learn a lot every day uh. I wish there were more things i could teach at this level of depth, but drone stuff definitely seems to be my neck, so well because you enjoy it and love it and thats what it takes. I am the living uh proof of angela duckworths grit book, but i still have lots to learn so thatll, never end thats, true until we end thats true, if youre interested in learning more about drone mapping, though, as a drone, new member, you do have access to Our comprehensive mapping class and over six hours of advanced mapping resources if you thrive in a more structured environment where you need a content, delivered at a specific pace at a specific sequence in chronological order, if that helps, you check out the props mapper program, i promise I think that you will be stunned, its also a quick reminder.

The props, mapper mapping class has been updated, and so it includes more information, so uh hope that you all enjoy that. I do say thank you for the question. Eduardo really do appreciate the level of detail, love, detailed questions. If you have a question, go to askdronenew.com, throw in some of those business questions throw in some of those creative questions. Theres a lot of news, probably hitting the market this week, thats going to affect all of us so its going to be very interesting. I know we also have a question uh regarding a remote id that came in regarding you know what drones to fly to fly over people etc, and i think we will get to that one. I will say, though, theres a slight delay on that, because ive really had an intellectual conundrum with rob about. How much does this really matter when things are being challenged when were getting new drones all the time and the market is just evolving so rapidly like? How much does it matter? So if youve thrown in a question, hasnt been answered yet it will get answered, but we do really appreciate those questions also last a little housekeeping. If you are a droneyou member and you havent downloaded the app yet highly recommend that you do so uh. The engagement is off the roof right now or its through the roof. Right now. Excuse me and uh yeah, to see like 30 to 50 notifications.

Every morning is actually really awesome because were uh, i feel like the engine is, is back on rob and uh yeah im grateful for that. So thank you to all you joining me members. If you havent downloaded the app download it at your convenience yeah, you might not even be aware that were not. The community is not on facebook anymore, which might excite you.