Litchi mission height question

[Chip D]

Yup. That was it. Why did that stupid thing get reset? I guess that's a function of the newest upgrade so I'll have to make sure I always reset it.
Thanks.

 

[53-63-6f-74-74]

Yup. That was it. Why did that stupid thing get reset? I guess that's a function of the newest upgrade so I'll have to make sure I always reset it.
Thanks.

Firmware updates can reset crucial settings without your knowledge.

 

[dwallersv]

There seems to be some misunderstanding.

Yes, there seems to be, but not what you think it is

[long, correct description of batch-editing waypoints to set ground-relative altitude elided...]
Both procedures have nothing to do with the home point elevation, other than it being used as a 'reference' by Litchi,

which was exactly the point of this thread!

It wasn't about how to get ground-relative waypoints. The issue was, what would happen with the altitude at those waypoints if taking off substantially lower than the first one.

The one-word answer is, disaster!

 

[dwallersv]

Okay guys, I took some time and made a video that hopefully will completely clear this business up regarding how Litchi interprets waypoint altitudes, and how to easily set up and manage a mission with ground-relative waypoints where the launch point may be unknown or change.

Take a look, and give me any feedback so I can improve it. If it makes no sense at all, I've got some work to do

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[JetexJim]

Well done dwallersv. You've illustrated the situation very thoroughly. I'll watch it again tomorrow and post any further thoughts.

 

[lisadoc]

Okay guys, I took some time and made a video that hopefully will completely clear this business up regarding how Litchi interprets waypoint altitudes, and how to easily set up and manage a mission with ground-relative waypoints where the launch point may be unknown or change.

Thanks for that video. I hope it helps people understand what I said originally to the OP, that heights are displayed in Litchi relative to the home point.

As a matter of intellectual curiosity, can someone explain a couple of things for me regarding Litchi, as I suspect that many folks would like to plot missions over ground height, not home point height.

1) If Litchi Mission Hub can display the same Google maps for mission planning as does the app, why don't they offer the same capabilities in the hub as the app (like batch editing, setting heights relative to ground height, etc.)? Seems like it wouldn't be that hard to implement and would further their efforts to allow you to mission plan on a PC (which I find far more productive and efficient). You're already connected to the Internet while planning on Mission Hub, so why the limited capabilities from those on the app?

2) Since Litchi can obviously calculate altitudes relative to ground height (when it allows you to edit points as "relative to ground height"), why can't it be planned as I suspect we all want as all points relative to ground height and be displayed as such, instead of insisting on displaying them as relative to the home point? There may be a reason for this but I'm missing it as I ponder the process.

 

[Logger]

...why can't it be planned ....as all points relative to ground height and be displayed as such, instead of insisting on displaying them as relative to the home point? There may be a reason for this but I'm missing it as I ponder the process.

Perhaps because it is considered a risky approach. Homepoint elevation is fact, every other point is derived from fallible terrain models or operator calcs.. It may also be limitation of the DJI flight plan mode.

 

[Simmmo]

Just like to say thank you to everyone who has taken time to reply to my question.

 

[dwallersv]

1) If Litchi Mission Hub can display the same Google maps for mission planning as does the app, why don't they offer the same capabilities in the hub as the app (like batch editing, setting heights relative to ground height, etc.)? Seems like it wouldn't be that hard to implement

That's undoubtedly the reason. Product/engineering priorities.

Yes, the technical/coding is not complicated or extensive in principle. However, to deploy as a supported customer product that would demand timely bug attention, it becomes an entirely different matter, and will consume not-insignificant resources to get it implemented, tested, and then provide on-going support.

I'm sure it's on the list of things to do, and will get there eventually. DJI has been throwing a lot of monkey wrenches into things with mandatory changes to the SDK, resulting in third party app providers having to spend engineering resources on things that were not part of the product road map. Have patience

2) Since Litchi can obviously calculate altitudes relative to ground height (when it allows you to edit points as "relative to ground height"), why can't it be planned as I suspect we all want as all points relative to ground height and be displayed as such, instead of insisting on displaying them as relative to the home point? There may be a reason for this but I'm missing it as I ponder the process.

Actually, so long as there's an internet connection there isn't any technical reason Litchi can't transparently handle all of this for us at take-off. It know's the location where you took off, so it can look up the ground elevation via Google services the same way it does when you set waypoints to ground-relative. This is all it needs to convert every WP altitude to the proper HP-relative altitude to get everything right.

Of course, this runs in to the same problem as with question 1 (resources), and as @Logger mentions, there's some considerable risk because the HP elevation may not be very accurate. A lot of things can mess this up -- like taking off from a tall building.

The way Litchi does it, the pilot is fully responsible for getting the altitudes right for the mission -- in total -- that they're flying.

 

[lisadoc]

The way Litchi does it, the pilot is fully responsible for getting the altitudes right for the mission -- in total -- that they're flying.

Actually, with the already-included calculation of "relative to ground height", Litchi is taking this determination on their shoulders (with reliance on the elevations provided by Google I assume). Not sure how that is any safer or better than simply allowing the user to create missions with the determinations of relative to ground height for all waypoints. Just wondering out loud...

 

[MAStetz]

Thanks to all that have posted in this topic, there is a lot of helpful info for a litchi beginner like me.

 

[marklyn]

Mission Hub won't let you do very much as of yet (I hope this changes at some point); It does not have terrain data associated with it, only 2-d orthographic photos from Google Earth. The Mavic defines it's take off point as zero and Litchi defines subsequent way-point elevations relative to that based on the terrain model in Google Earth. So, your first way-point is set relative to the home-point zero. This is why your first way-point should be set to where you take off from. The Litchi app way-point bubbles will show the altitude of each point above the home point, and each way-point will be the altitude above Google Earth terrain that you have chosen. The easiest way to exemplify this is to create a mission and go through the process. Create a RTG mission in Litchi, export it to CSV and use the CSV to KML converting tool I linked to above. Open it in Google Earth and you'll see that it works (create the mission using metric data or it will not convert properly). That's half the fun as far as I'm concerned. I'll spend quite a bit of time planning and tweaking missions that I'll probably never fly any time soon.

I have a question about what I underlined above... why would Litchi show the altitude relative to home point in waypoint bubbles instead of showing the altitude above ground for each waypoint? Why do I care about seeing my altitude for each waypoint above or below the altitude for my home point? I'm not trying to be snarky, I'm really curious.
I would much rather see that waypoint 5 is set to 300' above ground to clear a power line, building, etc., rather than see waypoint 5 is -5' (below home point).

 

[MAStetz]

I have a question about what I underlined above... why would Litchi show the altitude relative to home point in waypoint bubbles instead of showing the altitude above ground for each waypoint? Why do I care about seeing my altitude for each waypoint above or below the altitude for my home point? I'm not trying to be snarky, I'm really curious.
I would much rather see that waypoint 5 is set to 300' above ground to clear a power line, building, etc., rather than see waypoint 5 is -5' (below home point).

what i do is create my mission on the web, then i open the mission on my I pad mini do a select all waypoints edit then choose the altitude relative to ground. Then terrain elevations no longer matter, now i can fly up the side of a hill and remain 100' above ground.
there is a youtube video on it somewhere. i hope the website will one day integrate the same tools as the app.

 

[marklyn]

what i do is create my mission on the web, then i open the mission on my I pad mini do a select all waypoints edit then choose the altitude relative to ground. Then terrain elevations no longer matter, now i can fly up the side of a hill and remain 100' above ground.
there is a youtube video on it somewhere. i hope the website will one day integrate the same tools as the app.

I do that too but when I'm taking off from a 300' elevation and drop down into a valley that is 200' below me, it unnerves me to see the bubble say "-200'" . I guess it makes sense but it's hard to wrap my head around seeing negative altitude numbers (relative to take off point).

 

[wxperson]

Remember... you have to be careful and understand when you have waypoint 1 at 200 feet and waypoint 2 at 100 feet (for example).... half way between the 2 waypoints the drone will be at 150'... so plan accordingly when dealing with changing ground and tree elevations. I create more waypoints then needed if flying up or down a hill.

 

[marklyn]

yup. I always use google altitude and drop markers along the route to be sure I'm not flying over an unexpected hill.

 

[MAStetz]

I do that too but when I'm taking off from a 300' elevation and drop down into a valley that is 200' below me, it unnerves me to see the bubble say "-200'" . I guess it makes sense but it's hard to wrap my head around seeing negative altitude numbers (relative to take off point).

lmao!!! yeah i'd be a little nervous also. maybe we should suggest litchi put RTG in front of the number

 

[MAStetz]

Remember... you have to be careful and understand when you have waypoint 1 at 200 feet and waypoint 2 at 100 feet (for example).... half way between the 2 waypoints the drone will be at 150'... so plan accordingly when dealing with changing ground and tree elevations. I create more waypoints then needed if flying up or down a hill.

Correct! but more then likely your tree line down a hill will maintain itself, now if you were flying a hill side city it might be a different story. also it would be advisable to take a visual observation of the waypoint mission prior to creating the mission. one other thing i do is also fly the mission in "test" mode, which means i fly at or above 200' RTG and then judge my final altitude accordingly.
*Sidenote* if you want to change the altitude relative to ground at the mission site, you will need internet so it can pull the altitude data into the mission. Found that out first hand.

 

[baldwijm]

Thank you all for taking the time to go over this! Very helpful, especially the video! I've been trying to plan missions in the Mission Hub, and it looks like the app actually makes it easier (just need a bigger iPhone now ).