m2fkxy · HackerTrans

m2fkxy

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Bacon Ipsum – A Meatier Lorem Ipsum Generator

baconipsum.com

4 pointsby m2fkxy2 năm trước1 comments

Is Germany electricity generation cleaner than France's today?

isgermanyclean.today

4 pointsby m2fkxy3 năm trước5 comments

Carbon intensity of electricity production in Europe, year 2021

twitter.com

1 pointsby m2fkxy4 năm trước0 comments

comments

8 tháng trướcdiscuss

Mad dogs are MD-80s.

năm ngoáidiscuss

That's true. I have a bias of having part of my formal education quite focused on geospatial topics. Seeing non-geospatial folks reinventing wheels taught in GIS 101 both makes me smile and grimace thinking that we have have been doing something wrong with basic tools and aspects of the trade not being wider known.

You can look into TopoJSON here: https://github.com/topojson/topojson And a good general introduction to topology in GIS setting is nicely found in QGIS documentation: https://docs.qgis.org/3.40/en/docs/gentle_gis_introduction/t...

năm ngoáidiscuss

https://github.com/topojson/topojson

năm ngoáidiscuss

> A side effect of the geometry simplication is that there are some very small gaps between states. Based on your use case, you'll need to handle the case of the point not being within any state borders. In these rare cases, you could fall back to a different method, such as distance checking centroid points, adding an episilon to all state borders, or simply asking the user. (The user may also be in another country or in the ocean...)

This is a common topic and easily dealt with by working with topology-informed geometries; most simplification algorithms support topology handling between different features. For instance, TopoJSON can be used.

năm ngoáidiscuss

it depends on what flavour of English you speak. British English for instance tends to use plural for collective nouns.

năm ngoáidiscuss

This sounds like marshrutki. These are very common in post-Soviet countries to fill the demand left unmet by public transportation service.

năm ngoáidiscuss

the TCAS data would have been displayed. but not on instruments or in any place that you typically pay attention to the most during final visual approach (ie., mostly outside).

năm ngoáidiscuss

TCAS RAs are inhibited at low altitude.

2 năm trướcdiscuss

yeah, and then you need to get refreshed orbital elements for those satellites. not good if you are in an airtight environment.

celestial ephemerides don't change nearly as much.

2 năm trướcdiscuss

your point being?

2 năm trướcdiscuss

...which is obviously designed to be maximally visible from the public space.

2 năm trướcdiscuss

it's useless thence I love it.

I lied, in fact I just used it to create a couple Slack emojis.

2 năm trướcdiscuss

> Plausibly, there is no real monitoring of co-orbiting bodies in space

[capable] nations operating sensitive satellites and other space assets absolutely are monitoring foreign objects maneuvering in their orbital vicinity.

2 năm trướcdiscuss

not at all, I love it too

2 năm trướcdiscuss

it's also not the proper scale type for sequential data (red/green is diverging, but there is no central value defined in the linked map).

2 năm trướcdiscuss

  For those less obsessed with SAR images

Touché!

Also good point regarding multibounces and multipath. I would expect eg. landing gear returns to be standing out in those cases (cockpit too, although probably the canopy is coated to prevent radar penetrating).

2 năm trướcdiscuss

Yes, radar shadow is how you would find it. But your sensor must be performing well enough for it to be able to distinguish a shadow from the surface backscatter (ie. radar signature) the aircraft is sitting on. This is usually not a problem for rough surfaces (eg. grass or dirt, or some types of pavement), but it can be more problematic for surfaces with more specular scattering.

2 năm trướcdiscuss

A little nitpick about:

  The number of looks correlates with a higher resolution.

Yes and no. When you task an image, you usually (as is the case with Umbra) specify your desired ground resolution, eg. 25, 50, 100 cm, etc. There are two dimensions in a SAR image: range and azimuth. Range resolution is determined by the SAR system bandwidth. Azimuth resolution is determined by the integration angle (the angle formed between your target and your satellite from start to end of the collection).

Let's assume you want a 50 cm image. Your range resolution will be equal to that and, in a 1-look image, your native azimuth resolution will also be 50 cm. What happens when you request a multi-looked image, is that the satellite will collect data over your target for a longer amount of time (and thus over a greater angle diversity). Range resolution will not change; however, in the natural ("native") image, you get asymmetrical pixels: taking the same target resolution of 50 cm, a 2-looks image will have a 25 cm azimuth resolution. For 3-looks, ~16 cm. And so on.

What then happens during the processing of derived products (eg. GEC) is that the pixels are squared: to do that, you have to average out the pixels in the azimuth dimension. This greatly improves what is called the radiometric resolution (ie. how much information a pixel contains), by cancelling out the speckle and averaging the noise. But for all intents and purposes, on a multi-looked image (which is what the GEC products that you use are), spatial resolution remains the same, square pixel.

[SAR nerds here: I am not mentioning the slant-range-to-ground-range process, and I am also ignoring the resolution vs. sampling distinction for simplicity]

2 năm trướcdiscuss

yes, received power is inversely proportional to the distance squared. it's hard to overstate how ridiculously small the amounts of power are at play with spaceborne SAR systems.

2 năm trướcdiscuss

most complex and/or commercial aircraft do share the workload between a pilot-flying, and a pilot-non-flying—in addition to the captain & FO hierarchy you are probably aware of.