# 'slowness' error while using stream.ppoints()

**URL:** https://discourse.obspy.org/t/slowness-error-while-using-stream-ppoints/1008
**Category:** Related: rf
**Created:** [July 28, 2020, 1:17pm UTC](https://discourse.obspy.org/t/slowness-error-while-using-stream-ppoints/1008 "2020-07-28T13:17:00Z")
**Posts on this page:** 1
**Showing post:** 5

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### Author: ![trichter](https://discourse.obspy.org/user_avatar/discourse.obspy.org/trichter/32/226_2.png) [@trichter](https://discourse.obspy.org/u/trichter)
#### Post date: [July 28, 2020, 5:19pm UTC](https://discourse.obspy.org/t/slowness-error-while-using-stream-ppoints/1008/5 "2020-07-28T17:19:02Z")

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Yes the iasp model is used by default, but to calculate piercing points you need to know something about the incoming ray.

I think when you want to use rf in spyder, you need to install rf into the same environment spyder is installed in. You can check the installed packages with `conda list`.

> I couldn’t upload the SAC file “unauthorized”…

What a pitty, maybe we can improve on that, see [Upload attachments to post](https://discourse.obspy.org/t/upload-attachments-to-post/1009).

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