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rogerabc
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I've only just spotted this thread & for a long time have wanted to see spot heights on the top of high ground as shown on CAA half mil paper chart. Have you considered emailing out a questionnaire for desired features? On the subject of terrain clearance, I'd like to be able to set my own colours & thresholds for terrainsafe.
Many thanks for the great product.
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ckurz7000
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I wonder how useful an elevation read out really would be. There are different resolution elevation data available. If the data has a resolution of about 1 km x 1km then it isn't very useful at all. It could actually be potentially dangerous. You'd need it at least in a 10 times better resolution, like 100 m x 100 m. But that increases file size a 100 fold. That said, the best available elevation data has a resolution of 30 m x 30 m and is accurate to about +/- 10 m.
-- Chris.
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guille
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+xYes, that is what I currently do, but it means a lot of constant tapping and an extra equation, and when flying low level I'd rather minimise the workload and keep both hands on controls. Would also be useful for a few of the air racers out there that need to maintain a certain minimum height. I love SD, but find that getting any sort of current or spot elevations a frequent issue.Is it something that could maybe be considered but turned off by default? I agree with this request: when flying low, it is necessary to have a good precision concerning height, and getting directly the elevation of terrain would be great. Frequently I check the altitude measured by SkyDemon and by my altimeter and the differences are quite important.
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drnicolas
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+x+xYes, that is what I currently do, but it means a lot of constant tapping and an extra equation, and when flying low level I'd rather minimise the workload and keep both hands on controls. Would also be useful for a few of the air racers out there that need to maintain a certain minimum height. I love SD, but find that getting any sort of current or spot elevations a frequent issue.Is it something that could maybe be considered but turned off by default? I agree with this request: when flying low, it is necessary to have a good precision concerning height, and getting directly the elevation of terrain would be great. Frequently I check the altitude measured by SkyDemon and by my altimeter and the differences are quite important. Are you sure, that this can be achieved by a Software like SD? At first we Need a exact terrain-altitude-database with a small grid (see ckurz7000). Is that available? Second we need a good (true) altitude readout. AFAIK, plain old GPS is not a precise source for this. Is WAAS suitable for this? What about GALILEO? From the IFR Point of view all DAs für RNAV approaches are sginificantly higher than ILS and that is for LPV! Take EDVK: DA for ILS27 is 947 feet, while LOC27 is 1340ft - 400ft difference! For GPS, the LNAV MDA is 1340 (like LOC-Approach); with Support from your barometric altitude it is 1210ft - and that is temperature limited! Best GPS DA is for LPV27 with ~1100ft - even 160ft worse than ILS! I guess, the guys who made the approaches know, why GPS Needs significantly higher Minimums ! Can the barometric pressure sensor of the latest iPads (my mini 4 has one) be a solution ? I think not! It is not connected to a valid static port, it's inside the cabin. Just try what happens if you Switch to the alternate static source of your aircraft - it jumps up about 80ft or more! Okay. We are talking about VFR-sight-seeing, so this all may be tolerable
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guille
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Group: Forum Members
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+x+x+xYes, that is what I currently do, but it means a lot of constant tapping and an extra equation, and when flying low level I'd rather minimise the workload and keep both hands on controls. Would also be useful for a few of the air racers out there that need to maintain a certain minimum height. I love SD, but find that getting any sort of current or spot elevations a frequent issue.Is it something that could maybe be considered but turned off by default? I agree with this request: when flying low, it is necessary to have a good precision concerning height, and getting directly the elevation of terrain would be great. Frequently I check the altitude measured by SkyDemon and by my altimeter and the differences are quite important. Are you sure, that this can be achieved by a Software like SD? At first we Need a exact terrain-altitude-database with a small grid (see ckurz7000). Is that available? Second we need a good (true) altitude readout. AFAIK, plain old GPS is not a precise source for this. Is WAAS suitable for this? What about GALILEO? From the IFR Point of view all DAs für RNAV approaches are sginificantly higher than ILS and that is for LPV! Take EDVK: DA for ILS27 is 947 feet, while LOC27 is 1340ft - 400ft difference! For GPS, the LNAV MDA is 1340 (like LOC-Approach); with Support from your barometric altitude it is 1210ft - and that is temperature limited! Best GPS DA is for LPV27 with ~1100ft - even 160ft worse than ILS! I guess, the guys who made the approaches know, why GPS Needs significantly higher Minimums ! Can the barometric pressure sensor of the latest iPads (my mini 4 has one) be a solution ? I think not! It is not connected to a valid static port, it's inside the cabin. Just try what happens if you Switch to the alternate static source of your aircraft - it jumps up about 80ft or more! Okay. We are talking about VFR-sight-seeing, so this all may be tolerable I think SD has a good database concerning elevation. It can be clearly seen on the computer when preparing flights. And the idea is to use this database, combined with the horizontal position, that is also quite precise with the GPS included both in IPAD or ANDROID devices. The altitude of the barometric altimeter is also precise. So, if we combine the good altitude from the barometric altimeter with the good elevation from SD a simple substraction provides a quite good indication of height. Why not ? Some years ago I used a French software called NAVI that had this possibility and it was really useful. The button for time now has four indications ! and is very useful. Why not three for the altitude-height button ? But I don't know if the elevation Database is included in the Ipad and Android versions, that may be the problem perhaps.
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Gax
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"But I don't know if the elevation Database is included in the Ipad and Android versions, that may be the problem perhaps."
It would have to be, otherwise it wouldn't be able to calculate height
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Tim Dawson
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There's more than one kind of terrain data. We use 30 arc second data which has been specially created from 3 arc second data in order to give the maximum terrain heights; this works well for calculating MSA and keeping you well clear of terrain when using the height function of the altitude readout. We also use 3 arc second data in SkyDemon when you've downloaded high resolution terrain data. This creates more precise terrain relief shading in the background and if it's available, the height reading will use that instead of the former values.
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guille
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Group: Forum Members
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+xThere's more than one kind of terrain data. We use 30 arc second data which has been specially created from 3 arc second data in order to give the maximum terrain heights; this works well for calculating MSA and keeping you well clear of terrain when using the height function of the altitude readout. We also use 3 arc second data in SkyDemon when you've downloaded high resolution terrain data. This creates more precise terrain relief shading in the background and if it's available, the height reading will use that instead of the former values. Perhaps I am wrong, but the problem is the error for the altitude, compared to the one provided by a barometric altimeter. If I understand well, SD calculates Altitude minus Elevation for providing Height. Elevation measures are very good, the problem is with altitude. If we can have the elevation, a mental simple calculation could provide a very good estimation of height. I found sometimes differences of more than 200 ft between the figures provided by SD (ipad mini cellular) and the ones of the barometric altimeter. Anyway, it is just a suggestion, I believe it would be useful to have the elevation in the button of altitude/height. Even with the more precise high resolution terrain data, the error of the height measure will be originated by the altitude provided by the GPS-
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Tim Dawson
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True, but that sounds like you want a feature only because your particular device isn't giving you a very good GPS altitude. Have you considered getting a device that gives you a better altitude? An external dedicated GPS would do so.
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ckurz7000
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GPs derived altitude will always suffer variable errors. Accuracy in altidude is not as good as in lateral navigation. Therefore it is dangerous to rely on GPS altitude in mountainous terrain.
-- Chris.
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