Got Litchi recently, setting up a mission on Mission Hub. Waypoint #1 is at 33 feet altitude (almost directly above home), Hub shows ground elevation at 529 feet ,0 feet below 1st waypoint. Does this mean the Litchi ground elevation of 529 feet is at the 33 foot altitude or position of 1st waypoint? I would think the ground elevation would be from the home position. Thanks for any help
Litchi Mission Hub Ground Elevation
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From Litchi Help: "Waypoint Settings...Altitude: Waypoint altitude relative to the elevation of the aircraft where it took off." Positive and negative height of a waypoint and point of interest are relative to your takeoff point. Take off point is "0" so if your drone took off at an elevation of 529', your first way point would be 562' elevation or above sea level. I flew over 800' down a copper mine so I was over negative 800' down.
With the latest Android update you no longer need that procedure as it includes a 'relative to ground' setting in the batch editor function.
Even so it's a lot easier/faster to plot waypoints in Hub and then auto-adjust altitude in the app than using the Google Earth method, or at least it is for me.
I wrote Litchi, received a prompt reply regarding elevations. fttu is correct, it is elevation from the ground. Litchi reply: "In Mission Hub, the ground elevation is shown purely for information at this time." I got a topo map for the starting point of my waypoint mission. The topo map shows 670 feet, Litchi says 529 feet - difference of 141 feet. The Litchi elevation (which I assume is based on Google Earth) is way off. This makes me question even flying a mission in some areas (I live and will be flying with significant elevation changes) Any thoughts or suggestions?
The Google terrain database must have some error but 140 feet sounds like more than I would expect. Are you sure you were reading the contour lines on the topo correctly? If so there could also be a geocoding error and if the terrain was steep then a small horizontal error could equate to a significant altitude error. Bottom line, in rugged terrain you need to manually pre-run missions that are close to the ground to verify altitudes before trusting an automated mission.
Tops map read is good -verified by instrument. Great advice smiler! The elevation apps I have tried vary pretty wildly. How much elevation "fudge factor" is recommended in creating waypoints? I wonder how many crashes occur due to bad elevation information?
I think the Google terrain elevation is pretty decent actually, but you have to remember a few things. First, Google's terrain data truly is the ground contour without any buildings, trees, man-made berms, trucks, powerlines, etc. I noticed on some ponds and lakes that the terrain underneath the pond is in their database, rather than the water level. So your flight planning has to account for all that.
Tree canopy around here is about 140 ft, So I typically plan an altitude of at least 190 ft if I plan to fly over trees, plus the maximum ground deviation between all waypoints which can add another 100 ft or so. Then I round up to 300 ft as a starting point. I carefully examine the google earth (and some alternate imagery like bing maps or google maps too) to be sure I am not missing a powerline somewhere in the flight path. Be conservative on your first waypoint missions. Take a look at the video after you fly the mission and you'll get a good idea how much margin you really had. Adjust accordingly. Wash, Rinse,Repeat.
Tree canopy around here is about 140 ft, So I typically plan an altitude of at least 190 ft if I plan to fly over trees, plus the maximum ground deviation between all waypoints which can add another 100 ft or so. Then I round up to 300 ft as a starting point. I carefully examine the google earth (and some alternate imagery like bing maps or google maps too) to be sure I am not missing a powerline somewhere in the flight path. Be conservative on your first waypoint missions. Take a look at the video after you fly the mission and you'll get a good idea how much margin you really had. Adjust accordingly. Wash, Rinse,Repeat.
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They ought to scrap that old video. A waste if time and energy. Plan with Litchi Mission Hub and then batch convert RTG in the app. I found the elevations in Mission Hub to be accurate within a few feet checked with altimeter. This is probably a waste of time posting on an old thread. Well I'm an old guy so what the hey.
Yes, the new Litchi capability has been discussed in other threads. It is a nice addition. I like it. However, it does not really address all the concerns mentioned in the older posts above.
It's true that Litchi will now let us set waypoints with reference to ground elevations, AT the waypoints, but not along the path between waypoints. In terrain like the rolling hills of Virginia, it's sometimes very difficult to visually see the peak of the hill in the imagery in Mission Hub, and an elevation rise might be in the path between waypoints. So I always end up opening Google Earth so I can cursor through the entire mission path, to be sure my altitudes are sufficient to clear nearby elevation rises. Often I have to change the mission plan to set waypoints at those tops, just to be sure I clear them. Also the terrain elevation vagaries (trees, pond bottoms, etc) in Google Earth are still a problem with the new Litchi capability. Litchi doesn't have their own database; they rely on the same data in Google Earth to make their automatic conversions to AGL. Also, I still have to check for cultural obstructions like power lines, or towers or buildings. (Not so much a problem in the trivially easy terrain in the video above, but nearly always an issue in other areas, like the East coast, where we don't have those big sky views so much).
So even though I like the new Litchi capability, I find that I have to do almost the same work I had to do before it was introduced, particularly on long distance Litchi missions. The new Litchi feature still isn't a substitute for the KML file method using Google Earth above, because it doesn't consider the entire flight path, only waypoints. And I still have to at least manually cursor through Google Earth and double check calculated altitudes of everything in the flight path in Google Earth anyway.
But I'm not complaining, I like the new feature for other reasons. It certainly makes waypoint planning easier and more intuitive over relatively open terrain. It's easier to set altitudes above ground level for things like that, without having to do the math for conversion to home point reference altitude.
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My answer to your concerns is to click on the green Insert tab in the waypoint dialog box. Just keep adding them, drag them around to find suspected high points. But certainIy yes, do be aware of power lines and towers. I fly low altitude in Arizona mountainous terrain with high rocky crags all the time. I give plenty of clearance on first flight until I view the video. This works with me very well. I also have My Elevation GPS altimeter app on my tablet which shows Mission Hub altitudes correct within a few feet.
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Yes, many ways to skin a cat. If you have found a way to plan missions in a way that addresses your concerns, all is good. I'll probably stick with cursoring through Google Earth because it seems much easier to me. Most of my Litchi planning on long distance runs revolves around finding good camera angles for multiple POIs, which ultimately means trading off waypoint position, waypoint altitude, flight speed (for range), and fixed gimbal pitch settings, because gimbal pitch adjustments don't work in Litchi if you lose RC connection. So I always have a couple of tools like Google Earth open while I make those tradeoffs, which is very helpful for me, in addition to Litchi mission hub. Your case, with lots of open terrain, and easy ways to get high elevation takeoff/vantage points, is very different. To each his own.
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