# Order of radar rays in a sweep

**URL:** <https://openradar.discourse.group/t/order-of-radar-rays-in-a-sweep/630>\
**Category:** FM301 Data Standard\
**Tags:** data\
**Created:** [August 13, 2025, 1:28pm UTC](https://openradar.discourse.group/t/order-of-radar-rays-in-a-sweep/630 "2025-08-13T13:28:38Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![guntherhaase](https://yyz2.discourse-cdn.com/free1/user_avatar/openradar.discourse.group/guntherhaase/32/441_2.png) [@guntherhaase](https://openradar.discourse.group/u/guntherhaase)\
**Post date:** [August 13, 2025, 1:28pm UTC](https://openradar.discourse.group/t/order-of-radar-rays-in-a-sweep/630/1 "2025-08-13T13:28:38Z")

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Do you know if FM301 requires a specific order of radar rays in a sweep, e.g. based on time or angle? I could find any information on this in the documentation.

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**Author:** ![kmuehlbauer](https://yyz2.discourse-cdn.com/free1/user_avatar/openradar.discourse.group/kmuehlbauer/32/439_2.png) [@kmuehlbauer](https://openradar.discourse.group/u/kmuehlbauer)\
**Post date:** [August 13, 2025, 1:42pm UTC](https://openradar.discourse.group/t/order-of-radar-rays-in-a-sweep/630/2 "2025-08-13T13:42:10Z")

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Dear Gunther @guntherhaase, welcome on board openradar discourse!

As I read the documentation, it depends on how the volume is aquired:

```txt
301.4.2 Sweep groups shall be named sweep_, where is the sweep
           number starting at 0 for the first sweep acquired during the volume
           and increasing sequentially in acquisition order.

```

Taken from here:

[https://library.wmo.int/idurl/4/35625](https://library.wmo.int/idurl/4/35625)

Hope this sheds some light.

Best,  
Kai

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**Author:** ![kmuehlbauer](https://yyz2.discourse-cdn.com/free1/user_avatar/openradar.discourse.group/kmuehlbauer/32/439_2.png) [@kmuehlbauer](https://openradar.discourse.group/u/kmuehlbauer)\
**Post date:** [August 13, 2025, 1:44pm UTC](https://openradar.discourse.group/t/order-of-radar-rays-in-a-sweep/630/3 "2025-08-13T13:44:25Z")

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Hi again,

I see, that doesn’t really answer the question. But as `time` is the major dimension, I’d assume that rays are in order of acquisition, like in CfRadial1.

Update: There is a global attribute “Ray\_times\_increase” which can be set `true` or `false`. So it seems possible to have an arbitrary ray layout. Unfortunately the documentation isn’t very chatty about that feature.

Best,  
Kai

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**Author:** ![guntherhaase](https://yyz2.discourse-cdn.com/free1/user_avatar/openradar.discourse.group/guntherhaase/32/441_2.png) [@guntherhaase](https://openradar.discourse.group/u/guntherhaase)\
**Post date:** [August 13, 2025, 2:02pm UTC](https://openradar.discourse.group/t/order-of-radar-rays-in-a-sweep/630/4 "2025-08-13T14:02:05Z")

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Thank you, @kmuehlbauer!

Yes, that makes sense. But I’m not sure if this is intentional.

Best,  
Günther

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**Author:** ![DanielMichelson](https://yyz2.discourse-cdn.com/free1/user_avatar/openradar.discourse.group/danielmichelson/32/8_2.png) [@DanielMichelson](https://openradar.discourse.group/u/DanielMichelson)\
**Post date:** [September 2, 2025, 1:02pm UTC](https://openradar.discourse.group/t/order-of-radar-rays-in-a-sweep/630/5 "2025-09-02T13:02:35Z")

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Hi guys,

Let me look into this. Ray\_times\_increase=False seems counter-intuitive to me, but I’ll get clarity.

best, daniel